Did you get taken . . . how much is your life worth? There is always a chance that a dive shop is not doing the work it claims however I don’t think that they would be in business long if they did and the liability issues with doing substandard work could close even the biggest shops. Now for the cost; not knowing how old or the condition of the equipment as a minimum I expect that they put in an overhaul kit into the first and second stages. If any other hard parts were needed e.g. valves, springs etc. then it naturally adds to the cost. Considering that most overhaul kits with just soft parts, O Rings, diaphragms and the like start around $40 and go up, again depending on the type; as well as the other work completed then no you likely got a fair price. Additionally consider that if something goes wrong, needs adjustment as it free flows a bit to easy they would likely do this at no cost. Not a bad price for peace of mind. You could have had the Air2 repaired as well. My $.02