The price moved from $33 to $40 as he bought the shares[1]. THEN it moved from $40 to $50 when he announced that he bought the shares on April 4th.
Hard to say what the stock would have done without the purchase, but Musk has both the threat of dumping his shares on the market AND the threat of him announcing that he's dropping his shares. A case could be made that he has at least $17 of influence on share price, but my guess is that the market frenzy will drag it lower if Musk backs out.
Note: Please correct me if I misunderstand the meaning of the filing. I read it as Musk began buying up shares March 14th, and finished near the end of March, then reported Friday/Monday April 1/4. I don't think he bought and announced the same day. Musk owns ~73M shares, and trading volume was ~15M on the 13th, then jumps to ~35M/day over the next few days before settling down at ~15M/day again. https://finance.yahoo.com/chart/TWTR#eyJpbnRlcnZhbCI6ImRheSI...
What we do know is that it's not a 1 to 1 mathematical if one buys 9% it moves 10$ if one then sells 9% if falls $10. This has historically proven over and over.
