Just tell them you need an itemized statement. There is nothing wrong with that. If you ran your own business before I'm sure you know that.
If they think you don't trust them...oh well. It's your money.
Is it possible that the lineset "comes" in 30' increments so that they had to cut 10 off you're still being charged for the 30? If so, tell them you want the other 20. They can't charge you for what you don't receive.
lets do the math you say 4 hours @ 65.00 ==== 260.00
Line set 3/4 x 3/8 50 ft ==160.00 price of copper sells differant all over the place. place up the road wanted 225.00 for 50 ft
260====labor (my rates are 85.00 per hour)
10 ft 3/4 x 3/8 lineset at 3.20 per ft(his supplyer could cost more)
32.00====lineset 32.00 my price
50.00 ===== r-22 refrigerant 1 lbs my price (20 per lbs)
50.00===== nitrogen,vacum pump,acealene tank for brasing
25.00== brasing rods, copper fittings straping material,wiring
refrigerant reclaimer if used $$ not used
7% tax $29.19
grand total cost $$446.19