Surely for a startup this sort of information is not worth $10000? It just seems like you've got so many more important things to worry about than to worry if someone,s going to spend thousands of dollars figuring out how many users you have (which is likely an effect, not a cause, of any competitive advantage).
If Moore's law holds and you're willing to wait a month instead of ~9 days, it costs <$1500 in hardware, and you can keep/resell that. Or, again, rent time. Or just use a distributed.net-esque approach and bruteforce using (a lot of) standard PCs. Or...
Seriously, "people aren't going to hack us" is the new "premature optimization is the root of all evil": a convenient excuse to do it horribly wrong.
