MTG Finance and "Stocks"
For the purpose of trying to stay honest with prices this article is being written on 8/13/2020.
Welcome back! I wanted to touch on the topic of card prices and value today after seeing some interesting things happen on the internet this week. For those of you who are not aware, the American market is currently in the middle of an almost yearly Reserved List buyout/spike. There were multiple posts across social media talking about a spike of Gaea's Cradle and a bit of criticism of the MTG Finance community. Let's see if I can clarify a few things and try to help spread a bit of knowledge on properly valuing your cards or collection.
Graphs

If we look at the graph of Gaea's Cradle we are able to see the almost instant spike from the $500 range in May to a peak of $873 on August 10th. There is also another trend I want to point out - you can see the initial bump of the 2016, 2017, and 2018 follows the same trend of this past May. These are (for the most part) caused by a sudden interest in Reserved List cards. Many cards on the RL also follow the same trends, especially those that are popular in commander. Recent examples also include Gilded Drake, Helm of Obedience, and Memory Jar. Many of these price points and graphs can be found on popular sites like MTGGoldfish or MTGStocks, yet sometimes they can show different price points. The situation that happened this week was MTGGoldfish showing a price of just under $1000 for Cradle. Let's look a bit deeper at that though and we can find some truth to the values.
MTGGoldfish, much like other sites that host graphs and prices, takes it's data from popular sites to purchase and sell cards from. As for MTGGoldfish I am not 100% certain where all of their data comes from, but we can probably guesstimate that it's a combination of TCG Mid and Card Kingdom since those are two sites linked for purchase. If we go to TCGPlayer and look for non-judge promo Cradles we will find a number of shops with 1 card listed from $800-$1200 and a shop with 7 listed under $500. Had we looked at this a few days ago I guarantee you the majority of these shops would be closer to the $500 price point with one or two at the $900+ that had very recently posted. Sites like MTGStocks and MTGGoldfish will take those few shops with spiked price points into consideration since the data is all pulled as one source and it will manipulate the price point on these websites. If you watch MTGStocks you can see random cards that are less than $5 suddenly spike to $514 - that is explained as a store on TCGPlayer listing a card as a typo (often forgetting the a period in the price).
Resources and Due Diligence
Now that we understand how some of these graphs work we can do our DD to find a truer value of a card. There are a few different ways to go about this, some that are free and some that come at a price. I'll do my best to go into both, but you have to understand that there is always going to be information that isn't public about certain services.
MTGStocks FREE This is a great website to learn some initial or general information about a card. Their graphs are fairly accurate of a general trend, they follow the TCG Mid and TCG Market prices as well as the European average (which I believe comes from Card Market but I'm not 100% sure on that. Card Market is the European version of TCGPlayer). On top of the graphs, they post articles about the top three or four cards of the past week with information about why they may have spiked and specs to keep an eye on. You can find the current lowest or highest price point of a card, and the Interests page gives both daily and weekly price changes. The thing I like about this site is that I can find trends on foils as well as the TCG Market average for cards (which is a more realistic reference point than TCG Mid).
(TCG Market is what has been recently sold versus TCG Mid which is a current price listing.)
MTGGoldfish FREE
I've gone into most of what I know about MTGGoldfish, but I want to reiterate that you can gain some general knowledge about cards based on their graphs and Movers and Shakers section. This would be a site I would reference for my trade binder at an FNM or a casual situation. They also give you price points for decks which can be a great way to get a sense of what sealed product (such as Commander decks) might be worth.
EchoMTG FREE or SUBSCRIPTION
What a fantastic tool this website is! It's free to sign up if you wish, though you don't have to do so just to get general information. EchoMTG allows you to upload your collection and follow trends of cards you own for free (360 card limit) and with a tiered subscription you can upload more. The more you decide to pay for a subscription, the more information you have access to including mobile API access, emails for tracking and summary, text messages, trend analysis, and more. There is a bit more information that can be collected from EchoMTG as their data is pulled from multiple resources.

Trader Tools SUBSCRIPTION
Quiet Speculation is a fantastic resource for those of you looking to get deeper into the finance game. The website offers both free and paywall articles, a very active subscriber discord, collection tracker, Trader Tools, and the ION Scanner. Trader Tools is something developed specifically by QS and is a much more in-depth price evaluation resource. TT uses a large number of store websites and a lot more data is pulled in to get a much more realistic sell point as well as what many websites are currently buylisting cards at. Having both of those in once place gives you the ability to value your cards more accurately and to find a buy point that won't break your wallet (with a greater chance for profit if you are flipping cards). The ION Core is unique to QS as the developed it; it's software that you can use to scan your cards via webcam and automatically update your TT portfolio.
MTGPrice FREE/SUBSCRIPTION
MTGPrice is a great resource that is similar to EchoMTG where you can find free resources that pull from more data points such a trends, graphs, and articles, but it comes with slight restrictions. If you opt to become a ProTrader at $7.99 a month you get all of this information immediately upon release, as well as immediate access to their Podcast (MTGFastFinance) and discord access. Having access to some of that information before non-subscribers can be crucial. With store access at our finger tips card buyouts can happen almost instantly and spikes can occur within hours.
Conclusion
I hope I've helped give a bit of insight into why certain things happen with price points and how you can try to be on top of them. I'm going to elaborate on a few things such as the Reserved List, alternate forms of buying, and functional reprints in future articles and they can all come back to some of this information. Understanding the actual value of a card can be very important. As always if you have questions or would like to discuss anything further you can find me in The Lotus Council's discord as well as Twitter. Until next time fellow gamers!