Sorry, my mistake. I was looking at the wrong receipt.
They were closer to $100/tire. I get mine from Frisby.
And yes, I did pay $65/tire for my first set, back in 1998. They lasted quite a while. Had to finally toss them at the start of last season due to dryrot in the sidewalls, otherwise I had about 50% tread left. They got used about 10 times during that period.
I agree with Kirk, for the most point, but one other very important issue is temperature. It can be damp but cold and the surface will be like ice, and without grip, you can't get the tires to work hard enough to generate heat, in order to generate grip.
My criteria for when to use them is whether or not the cars in the previous race group are giving off lots of spray on the straights. Obviously temperature, wind, sunlight, and age and type of track surface are other factors that determine when to run wets vs dries. Local track knowledge helps a great deal in this respect. Some tracks will start to dry as soon as it stops raining. Other tracks have to be almost bone dry before you get any grip at all. Tracks with lots of trees in some sections will tend to take longer to dry due to the trees blocking the sun, plus the rain will drip off the leaves onto the track.
And then there's always the fun of running a real long track like Road America and have bright sunshine and clear sky in turn 1, and a thunderstorm in turn 12.
