My estimate is around $100 for a full set, maybe a little less. I am shipping a set of Goodyear Eagle F1's 295/45-18 from Michigan to New York for about that much. The Hoosier's are lighter (less $) but a longer distance (more $).
I have a set of these now from another supplier and ran them for the first time two weeks ago. It was in the upper 40's the first session and it took a long time to get them warmed up and sticky. In the 2nd and 3rd sessions it was in the 50's & 60's and they warmed up much quicker. My fastest lap was always the last lap in every session so I bet that they are even better in 70+ degree weather. They are an endurance tire made to last for up to two hours of racing. Much better than the Falken Azenis RT615s I was running. Can't wait to get on them next spring when it's warmer. I am done for the winter.
They should have some used Mustang Challenge BFG R1's, 245/40-18. If you are interested email them. If they don't get back with you in a reasonable amount of time let me know and I will call and harass them for you.:-D