I did some research on what it would take to put in a central compressed air system here.
TLDR version: A roll of 1" ADS 200PSI polyethylene line for $224, maybe 5x tees (5x $4.43=$22.15 ) and 5x quick-disconnect couplers (5x $4=$20). Unknowns are how to couple the pipe to the quick-disconnect (and the cost), and where to put the compressor in all of this. Slight question on whether 3/4" or 1" is best. But basically in the $300 range.
First discovery was PVC is definitely out. Just about every link said "people have done it, but DON'T DO IT". In some cases it shatters. There's a requirement in many standards that PVC carrying compressed air must be completely enclosed for safety, which blows the budget beyond all reason.
Copper is recommended, but it's expensive. It HAS to be Type L for this, which is $2.42 per linear ft if it's 3/4", and $3.60/ft for 1".
So next on the list is polyethylene pipe. There's an "ADS" product at Home Depot/Lowe's good for 200 PSI, either 3/4" or 1" are on the table.
Which would of course be limited to 200PSI. This is fine, usually we regulate the usage at the hose to like 30PSI-125PSI. These can also be had in 100ft, 200ft, 300ft, 600ft rolls with the cost/ft only a bit elevated in smaller sizes. I cannot say exactly what length we need without a specific floorplan, probably to each wall of the big room and a line to #306.
I still don't know if we need 3/4" or 1", it depends on CFM usage and distance. Since the price is close, I'd be inclined to just go 1". I don't even know if we're talking OD or ID here. PE pipe is slicked than copper, which I saw people saying actually reduces flow restriction. PE pipe cannot be glued like PVC. Many of the common barbs are only 100PSI, but the "SharkBite" brand is 200PSI. They connect much easier than soldering copper pipe in-situ. They use pipe clamps to stay on.
3/4" tee, 200PSI for $2.46: http://www.homedepot.com/p/SharkBite-3-4-in-Plastic-Barb-Tee-UP370A/202300098#.UeOjakHCab8 And it's almost the same price in brass, $2.59: http://www.homedepot.com/p/SharkBite-3-4-in-Barb-Tee-UC370A/202032878#.UeOkAEHCab8
I don't see 1" Sharkbite parts in plastic at all though. If it's 1", it's a $4.43 brass tee: http://www.homedepot.com/p/SharkBite-1-in-Brass-Barb-Tee-UC374A/202032879#.UeOkU0HCab8 And a 1" $2.94 brass coupler (which you don't need unless adding more line later): http://www.homedepot.com/p/SharkBite-1-in-x-1-in-Brass-Barb-x-Barb-Coupling-UC020A/202032866#.UeOkiUHCab8
Then $4 for a quick disconnect 1/4" female: http://www.harborfreight.com/14-female-brass-universal-coupler-68182.html
Well but I'm not sure how to get from 1" (or 3/4", for that matter) PE line into 1/4" thread, either male of female. I'm not sure where the compressor would ultimately go, but the system would really allow it to be coupled in anywhere. One of our neighbors put their compressor outside, in the parking lot, just under a little hutch to shelter it from rain and sun. Not even a cage to inhibit theft, but it hasn't been stolen, so the security guard thing must be working. But to do so would require a wall penetration and customer shutoff box installation, so, "not easy to do cheap".