That depends on what the going rate for an arm and a leg is right now.
Kidding aside, Microsoft sets a standard price that all retailers are contractually obligated to follow. So if you want a legal version (and that's the only kind you'll get help in finding here) then you're kind of stuck. You can pay what Microsoft asks, pay even more for an MSDN account, or if you happen to attend an educational institution that has a partnership with Microsoft, you can usually get an academic version for very cheap. Of course the academic version's license will expire when you leave that institution, so take that into account.
Every now and then you will find some retailer selling copies a little below what Microsoft requires, but usually not by too much. You might be able to get it with only an arm OR a leg.
how and where can i get a windows 7 install disk without paying a arm and leg for it