Well, I got the bed of my pickup(Dodge Ram) done with Rhino Liner and I believe it cost me about $450, but that was 10 years ago. $650 doesn't seem too far fetched. As for the thickness, mine wasn't very thick either and I was a bit disappointed. Hopefully you got it done at a reputable dealer cause I believe Line-X is lifetime warranty also. At least this way if it chips or anything you can go back and have it touched up.
IMHO, had there been more choices back then, like Monstaliner, I probably would've done it myself. I did the tub of my Jeep with Herculiner and it came out very nice.