A single F-22 might be worth ten F-15s but 2,500 F-15s beat 180 F-22s all day.
You assert that, but do they really?
2500 F-15's require 2500 pilots,
Per flight hour maintance cost on an F-22 are about 68k per hour vs the F-15's 42k per hour. If you figure an average 200 flight hours per pilot per year, your plan cost the tax payers an extra 33 billion per year just in flight hours, not counting initial pilot training, pay, benefits, and facilities cost for the extra 2,320 airframes.
So when you consider the total cost of ownership for the capabilities imparted, your "cheap" F-15's are not looking so cheap any more.