You still have a mathematical error in your calculations. You need to divide the 1% inflation between 70-90 BP's getting paid. Let us say that the top 30 get 70% of the 1% in a year, that is 0.7% divided between all of them. If all of them collude to only vote for each-other and save all their rewards, you still end up with 0.7% of the votes against the current 10-12% all of the top 21 have.

I would say dpos inflation is more similar to PoW than you are describing - in where the input is the labor, electricity, infra costs - but only elected BP's can do the mining for obvious reasons (excellent speed and reliability). So we end with the token-holders/developers having to buy 70 to 100% of block rewards and offsetting the inflation benefits BP's are gaining.

This makes EOS not really a closed system, since there is an offsetting loop required for it to run - the market where BP's can sell their tokens for whichever currency they use to pay their expenses and developers/investors buying these tokens to gain resources on the network.