The trick with buying XX is to enroll your buddies who are still shooting bl/w film. If you get enough of them willing to chip in - buy a case load - either 10 or 20 reels of 400 ft stock. It is a high initial outlay, but look on the bright side - you wont be buying film for quite a while. So 20 rolls of 400ft of XX is $2500 + - BUT it also represents 1400 rolls of 37-38 exp film!
I am down to 7 cans at the moment and I think I will celebrate the New Year by stocking up on at least 10-15 cans ( at least 5 that will go to friends anyway).
The 400' can sounds a lot - but 70 rolls does not last that long and I also find that the fact that you have a lot of film on hand, also mean that you shoot more and thus get more and better pictures to work from.
I rather forego another lens or camera body for more film anyway!