tarmac rally tyers, last set i picked up for a mate were £ 160 for 4 fitted.
as they arrn't road legal they seem to be a lot cheeper for what they are, they are avalible as new or remoulds obviously the remoulds are quite a lot cheeper but they work well. avalible in loads of compounds and tread patterns or as slicks
the issue is finding someone who stocks them those that do don't advertise it much ether except in local motorsport mags so can take a bit of finding, they can be sods to fit on the rims unless theyve been warmed so if buy unfitted be careful who fits them. sizes they come in can be limuted due to what events the local motorsport clubs run but 195/5015 and 205 /50/15 can normaly be found without much bother