I'll throw you some thoughts on this. The price is so variable, its hard to say. You did not really discuss if you are looking for light, medium or heavy duty, so that is a factor.
Generically....
I picked up a set of forks that were actually old forklift forks that someone welded a QA plate to. They are very strong and I paid about $100 for them.
I was at an auction a month or so ago that were selling new sets for around $250 that looked like ones being offered on Ebay using buy it now for $748
They looked like auction number 390015976008 on ebay right now.
Simlar sets being auctioned on ebay are lower but still running (auction number 180365002368).
If you want cheap, go to a scrap metal yard as they often have sets sitting around that you can pickup cheap and then weld on a QA plate.
Hope this helps.