What is the $17,000 estimate for? Read your questions, you give us ZERO information.

So you have 6 sets of pw/awn combo units for 12 total units. Then, you have a cut-in AC unit being installed, including the electrical lines and everything?

As MWM said, there are way to many details missing here to say if that is high or not. In addition, I have no clue what an AC unit like that costs.
What I can say, is that the windows should probably run somewhere between $500-$900 per unit (x12) depending on options, install circumstances, etc. Could be more if they are loaded up with options, full frame tear-outs, etc, but for normal circumstances, I wouldn't expect that the window portion would account for more than maybe $10k on the higher end.

My suggestion: get a couple more quotes. That will be your best way to compare.... Then come back here and present more details on the products, install, etc, and we can give you some direction on what might be the best choice. :)