Depending on class rules, you can always look into buying a set of "used" tires from a pro driver source.
I was buying Hoosier DOT full race tires for $75 when new were $225, they only had one weekend on them and would last usually another 4-5 weekends, this was full w2w track racing.
Try Appalachian Tire, they never did me wrong had great prices and shipped out quickly
http://usedracetire.com/