According to your criteria, you're thinking more of 'potentially world class', which I guess is more in line with your price range. The world class guys work for Google.
Depends on your budget and appetite for risk. If you have the budget and want to reduce your risk, IMHO there's no better indicator of future performance than past performance.
Are you saying people with great track records are likely to be very unproductive? That seems unlikely ...
I've got a pretty good track record. How do I get to work in your world? :-)
IME, for regular employees, the difference in pay between a respectable senior developer, technical lead or project architect and a junior developer straight out of university is perhaps a factor of 3-4x. Unless you go into management and rise to a senior level, it pretty much plateaus after that in most places.
On the other hand, the difference in productivity between the same types of people can be a lot more than 3-4x. By the time you factor in the improved communications and general reduction in overheads from having a smaller team of individually more productive people, top people are easily worth a disproportionate amount, if only you can find them and convince them to work for your company instead of someone else's (including their own).