Looking at various stock (TSLA in the picture below on May 19, 2023) pre and post market trading graphs, I can nearly every day see some huge variations, way over market fluctuations, which I think do not make any sense (in the example below, we see back & forth jumps of +54.91% and -53.32%, even when we last saw TSLA taking a hit, it was not even -20% and it took a good hour to happen).
Looking at some other graphs (Google/Ameritrade/E*Trade), I do not see these variations making me think it's just a small glitch in the Yahoo! Finance display (although doing a reload doesn't fix anything, so the funky data would be on Yahoo!'s servers too).
So my question is: Should I ignore those extra-ordinary fluctuations? Or are these real (just too small to be shown on other services)?
The picture shows that the closing price was 180.14. After hours, it stayed pretty stable around 180.01 and 179.99. However, at 05:01 PM, as we can see on the left, the price jumped all the way to 278.84 and at 05:03 PM also down to $117.40. These numbers don't seem to make sense when the stock is currently traded at about $180. Why would someone sell at $117.40 when they could get an extra $63/share or buy at $278 when they could save nearly $100 buying that same stock?
I can confirm D. Stanley statement (in the first comment below) that those are not real. I now have the ability to place buy/sale orders in pre- & post-markets so I've tested and clearly, I am not able to buy stock at such a discounted price or sell at such a high price when it is just a dot on a graph as shown above.
I actually tested with several different values and each time those numbers were either below (buy) or over (sell) my price and 0 share were bought or sold.
So clearly these are spurious data that should be ignored.
What I do find surprising is that it happens on all platforms (Yahoo!, Google, Ameritrade, Schwab for those where I saw this happen).
Update 2025-05-22
I found the following page which has two answers and more comments about what can happen. Although as I mentioned above, I was not able to buy and/or sell at those crazy prices. So I still strongly think that these are errors. It just amazes me that there would be so many on a daily basis.
What could be the cause of a extreme high/low price in after hours market?
