You may be right, especially with the growth of applications of software. Personally I'd rather bet on slower revenue growth than the current 30%. Not necessarily much slower, but even 25% yearly growth over 10 years would be a big difference in the end compared to 30%. My thinking is that usage of cloud compute can grow greatly, but with revenues growth lagging behind, because of falling costs of compute (more powerful/efficient CPUs etc), economies of scale, and competition putting pressure on prices. For example AWS operating margin is 34% currently, I expect that to fall as the market matures (but Google's cloud margins are much lower right now).

Ok, let's say 25% growth over 10 years. That is a factor of 9.

9*$50B = $450B yearly revenue.

What could be the margin Alphabet makes from that? Last quarter, Alphabet had $100B revenue and $35B net income. So 35% margin.

$450Bx0.35 = $158B

What is $158B in annual profit worth? Currently Alphabet's p/e is about 30. If we take that, it would be $158Bx30 = $4740B. So around $5T.

If we are heading towards the creation of $5T in value via cloud revenue, investing $100B per year to build it seems not particularly high to me.