Are most A/C repairmen honest when it comes to the amount of freon they charge you for?

Given your a/c is being worked on in March, its likely you have a large cooling unit needed for your summers where ever you are. 8 lbs sounds normal IF it all leaked out, IF the leak wasn't fixed expect to do this again. $29.00 is fair. I've never ran into guys lying about the amount, bigger problem is usually the tech finding the leak, sometimes its due to laziness or times its due to a leak that seems impossible to find or sometimes it cannot be found, ex - a leak in the line set which runs underground, or a refrigerant line buried in the wall.