Am I missing something, or is Dektol expensive? Going by Ag's prices, 3.8L of Dektol (mixes up to about 12L at working strength) is GBP11. 5L of Multigrade Dev is GBP20, which mixes out to 50L or 75L. For most people, the dev will be discarded after a session so Multigrade is 2-3x cheaper per session.
Obviously, I use Multigrade. It doesn't help that that (and PQ Universal) are the only paper devs I've actually seen in a shop here in AU.
Edit: oops, it looks like it's the other way around if one shops at B&H. *ponders*...