Hypermiling, I'd expect at least 15-20,000 miles out of a $100-120 set of two tires.
"Economy" touring tires are priced @ $50/tire (~$100-120 per tire in car mileage terms). Since you only need two of them, the tires are essentially $50-60 "car" tires. The cheapest car tires I've ever seen were on-sale R13 tires for ~$30.
Good point about the tire issue, but I think its the bike junkie, ripping up performance tires in the twisties, that gives motorcycle tire tread wear a bad name...
- LostCause