I only agree with half of what is being said about it being not worth while.
I agree that it is not worth it to go as far as compresing the CO2 to a liquid but going up to 30-60 psi sould be achievable reasonably easily.
I was thinking about this only a week ago.
If you connected up your fermenter(s), check valve on each supply line so new brews arn't hit with high pressure straight away, to a "tank" (corny or sanke keg),
then from that go through a filter then into a small cheap compressor (like those 12V tyre pumps),
from there into another "tank" sanke keg,
finally supply your (secondary/low pressure) regulator from here.
If you wanted to go all out you could automate the pump to run off a pressure sensor so the first tank stays around 10-15 psi (or whatever you want) or just keep an eye on it (put a PRV on it somewhere so you don't kill your yeast/self
).
a 15 gallon sanke should hold enough CO2 @ 60 psi to push at least 10x 5 gallon cornies (shouldn't need to carb them as that would be done during the fermentation stage).
Go 1000 posts!