My company owns several websites and iOs apps that target, largely, the math education niche.
You will see that, for the most part, I have given my contractors all 5 star ratings (though there are exceptions). This is because I spend a lot of time trying to find the right people here on Elance for each job--this means I do value what your feedback on Elance has been and I will read your job proposal carefully. Please don't send me cut and paste generic proposals. Instead, I look for proposals that show that you've understood the job requirements and are up to the task.
Regarding hourly fees, I know, all too well, that an hourly fee can be quite misleading. $15 an hour by an inefficient developer who introduces bugs is always more expensive, in the grand scheme of things, than $50 an hour that a more efficient developer charges.