VLP is a program for free access to some IBM hardware (and software), but as far as i know it is limited to IBM partners. I might be wrong, though. It is meant for testing purposes ("does my code compile/run on the new Power 7+ processor?") and the like.
The prices from the link DGPickett provided seem a bit steep IMHO.
GALL (a german second-hand shop for workstations) has 43ps for as little as EUR 150,-, but beware: the r/6000 hardware is only able to run AIX 5.1! Later versions require p-Series systems.
I hope this helps.
bakunin