Or Megaman gradually bought Redymare (eg he already owned 50% and then bough out the other 50%, in which case that 50% was already accounted for in the stock price of Megaman before the buy out.

While Bassman might have bought out Razzk in one go (going from 0% to 100% in the buyout)

Looking at the graph my estimates of the percentages might not be to far off.

And looking at the faint text in the background, that Megaman bought out Bassman makes it probable: Bassman had to spend far more cash to buy out Razzk than Megaman had to spend buying out Redymare, which gave him to more cash left over to then buy Bassman.