You're in a straight truck, right??
If so, $1600-$2000 would sound about right.
The cab portion of a atraight truck has a lot of little hinges, brackets, and marker lights that either have to be removed or taped off. There will be some awkward work involving ladders and stools trying to get it all sanded down and prepped for paint. And then the painter will have a few awkward moves he has to make himself to be able lay the paint down smooth and even while on those same stools and ladders.
I trust you went to a reputable place that has an actual "Truck" paint booth there to spray the truck in the booth, right? If you just went to regular body shop and got these quotes, your truck is either going to sprayed in a big warehouse without the proper filtration in place, or outside in the parking lot after hours when all the city code enforcers have already clocked out and gone home. If this is the case, inspect truck very carefully for "Trash" in the paint. (small particles of dust & debris showing through the clear) If you see this, have them sand that crap out and rebuff the clear.
Also, another question comes mind. Are these quotes given for a commercial grade "single stage" paint job? (Single Stage - paint and clear together formula where you spray once and buff it out) Or have you been quoted for a "Basecoat Clearcoat" paint job? (BC/CC - color sprayed first then clear sprayed over it) My bet it's for a Single Stage paint job at that price, of which there's nothing wrong with it. Really depends on what brand they're using and how well they buff it out. Just make sure it's not something like PPG's "OMNI" label, or Dupont's "Nason" series if they're using a name brand paint. These 2 series are on the low end of the chart and may last you 2-3 years being out on the open elements 24/7/365. Try to get them to spray Sherwin Williams commercial grade paint if they can. SW has a GREAT lineup of paint for commercial use. Dupont and PPG's main focus is for the every day commuter car or truck.
If anything else comes to mind, I'll say something later.