The peak pressures are very high indeed; high enough that there will be some metal-to-metal contact in a chain bushing when a rider is really going for it.
Fortunately most riders are not pushing hard on the pedals all the time so average loads are smaller, and most clean lubes have some chance of separating the surfaces at least some of the time.
One thing is sure; without lube, a chain will be worn out in no time. Recently an LBS asked me to examine a chain that a rider had worn out in less than 200 miles. There was nothing wrong with the hardness of the pins etc, it is just that the rider had believed some fairy stories about how the lube on new chains 'is no good' and had carefully degreased the chain. He had then attempted to lubricate it with something that had failed to penetrate the bushings, leaving them bone dry. The wear rate was about x10 faster than normal.
In a test of chain transmission efficiency (you can read yourself by exploring the IHPVA archive) some researchers claimed that a degreased chain ran almost as efficiently as a lubricated one. It is almost certain that there was some flaw in this result, for example they may have used a Dura-Ace chain which has a baked on PTFE coating.
In all the published tests of chain wear that I have seen, the initial rate of wear is very low, and then increases after a few hundred miles. I think this may be because the factory grease works well for a while and then gets dirty/loaded up with wear debris. At that stage if you were to clean and regrease a chain, you might restore the low initial wear rate again.
cheers