You got valves and lines priced into your set up?
They can add quite a bit of cost.
You are right, just like buying a package holiday, if you get someone else to do all the behind the scenes work you are going to pay for it.
Make sure you are looking at a high duty pump though, some of the cheap ones are 1/20 duty which means for every 1 min the spend pumping they need 20 mins off (mostly to cool down) so you can end up bustin some moves on the street and no air in the tank - compresor tripped out from heat an you are sat unable to drive with egg on your face...
There are compressors available now that are 1/1 or 100% duty cycle and if you are not looking for fast air, you can get away without a tank.
Don't let my ramblings put you off though, get the system you can afford and get it in there!
PT's look so good on the deck.