I'm a little late to the answer suite, but I've hit more in the past year than ever. We hit 4 this past year. It pretty much impossible to climb in every attic and try to find an AC line that's bent or soldered into a 45, up against the deck. If you're wondering what I do? First I kick the tires off the truck and piss and moan about the person that installed it that way. Try to convince myself its not my fault, but it is my problem.
I fix everyone of them by calling the AC guy, but I always tell the owner that the AC guy did a poor job of installing the lines. You have to remember, these are usually drilled through the top plate and bent towards the attic, so that area is very hard to get to when bidding a roof.
Small units usually run me about $400-$600 for a repair, vacuum and charge. The scary thing now is the last one, cost us $1600 because it was a 5 ton, R22 unit. Called 2 guys to ask how much they charged for a pound of the gold, when my guy said $90 a pound. When the new proposals went out, I placed another addendum to the list, about AC and water lines that are placed too close to the deck that they are subject to being hit by a nail. Now it might be an uphill battle, but when you sign my contract, you've agreed that you've read and understand what your signing. At least I have something to fall back on if I hit an R22 line, a year from now and it's $200 a pound. It's frustrating.