in my area, i can pick up a used 27" wheelset inclyding freewheel for 80-100. havent compared prices to new wheels. a new 6 or 7 speed freewheel ie 14-28 is about 25. if i wanted to do 700c conversion price is same but id have to replace the brakes with longer reach ones. re finding used wheels it takes some patience for them to come up, so i look for backups before i need them. for instance i have a pair of 700c wheels off a miyata touring bike i paid 60 dollars for in good condition. these deals come along as people convert bikes to fixies or upgrade to 10 speed wheels.