depends a bit on th track day org as to who is used , i was recently quoted 230 for diablo slicks at brands, or i could get some others cant remember exactly what they were for 170. check with your tdo or check out their website and find out via the tyre man whos going to be there
I went to BH yesterday with FE. The first thing they mentioned in the Rider Briefing was their tyre sales chap and the photoman and suspension man...
I saw they were selling used slicks for about £35 a pop...I thought that would be a good deal if you just fancied trying slicks to see what they are like. I can't vouch for the condition but they looked well worn*.
BTW - had a great time, warm and sunny and no mishaps! My araldite and bacofoil repair held out a treat too!