I usually see grip installs being 2-3 dollars per club. This includes removing old grips by cutting them off.
But you asked about blowing the grip off , to save it I assume. They will usually do this for free if you are going to pay them to install new grips.
But you mentioned that you are trying to save Winn grips, I have been told many times that Winn grips are very difficult to save and they might not be able to do it. I saw one guy try to save a winn grip on my burner 2.0 and the cap of the grip flew right off. when he turned on the air.