I've been thinking about this one a bit. I understand with the problem it's addressing and am not opposed to fixing it, but I want to find another way of doing it. My issues with this particular solution are: 1) It will probably be less obvious floors are influencing costs than character levels, 2) It will eliminate any differences in costs between characters, upgrading your lower level guys would be just as expensive as your Anomaly Shoggth, 3) Weird edge cases like returning to the Tower after a 3 floor branch like Anomaly.. when you return from Anomaly, you return to a significantly "lower" floor of the Tower, but now have credits from 3 higher floors.
#2 in particular is a bit troublesome because one of the sneakier parts of the currency system is that you can, if you get in trouble, recruit a low level demon and train it up fairly cheaply. It is true this also allows some minor manipulation of currency has we've discussed in other threads, but I think this advantage outweighs that minor problem for the moment.
I will think on this for a bit and see if I can come up with a fix that doesn't run into those problems.
Feel free to make other suggestions in that line yourselves too, of course, and thanks for the feedback.