Plus we are forgetting one critical component in this scenario of yours which has been overlooked here repeatedly. The challenges. You'll be getting 10,000+ of them about every minute, 166 of them a second, and none of them will be the same and they are significant work. You'll have to hit the DB and do the work because you can't cache all the data, plus then the processing and creating the solution proof.
And you still havent acknowledged the pipe cost.
That's like a busy website, but it isn't going to break the bank. This is a major flaw with this design, I'm sorry to say.
You can fix it, though - and I've mentioned this before, throw away the trust model and use POW for voting on transactions.