The most egregious aspect is that these companies arguably shouldn't even have the ability to make such large purchases. They don't pay their taxes (using loopholes to appear completely unprofitable while an entity that is all-but-legally indistinct amasses a massive warchest is tantamount to tax avoidance, period) and they shortchange users on the value of their data (delivering software worth a fraction of the value of the data collected during its use). What results is an enormous economic distortion that has numerous negative effects, of which the issue described above is just one.
The situation is way more severe than this makes it sound:
* The benefit you get from $10b is not actually 200 times as much as the benefit of $50m. (Economists would talk of a "utility function" - that's what you should actually be taking the expectation of - and what I'm saying is that it's nonlinear.) How much it's worth very much depends on your personality, but for most people (maybe all?) it's worth well under twice as much, maybe barely 10% more? Either way, you never have to work again, and maybe your kids never have to work again, and you can enjoy your lifetime retirement in a great deal of luxury, so the difference in experience is minimal. It's probably not a big deal if you have to be careful not to charter private jets too often. So even if the chance of getting $10b is 1 in 10, or even 3 in 4, you still might find the $50m option wins.
* The $50m is right now whereas the $10b dollar requires effort. Not just 9-to-5 effort either, but possibly a CEO-of-a-startup 90-hours-a-week effort. Again, the benefit of $10b is not actually that much compared to $50m, so you might consider that marginal benefit less than than the extra work. If that's so, you would take the money now even if the big win were 100% guaranteed!