Since I do both small tank processing and intermittent large tank 4x5 processing, I use replenished developer since I need 1.75L of solution to fill my tank. Currently I use D23, but in search of more shadow speed for handheld work I was planning on switching to replenished Xtol. However I just did some quick math that shows replenishing Xtol doesn't actually save any money or chemicals over diluting and using one-shot.
When I develop in a 250mL small tank, using Xtol 1+1, I use 125mL of stock. This isn't much more than the 100mL of stock I would use if I was replenishing, so no solution saved there. If I used 1+2, one-shot would actually use less developer in the long term than replenishing.
When I develop in a large tank, using Xtol 1+2, I only use 580mL of stock, which is only $1.25 or so worth of developer, and I get times of over 10 minutes which promotes even development. Stock Xtol gives times of only 5-6 minutes. True, replenishing would be more economical if I developed only a few sheets at a time, but if I develop 20 sheets to a batch is the break-even point where I'm not saving any money replenishing compared to using 1+2 in my tank at all. Plus, some people are recommending replenishing every couple weeks even if I don't develop any film, and that quickly overwhelms any small savings that replenishment would give to smaller batch sizes.
So, for my way of working, it seems like I will get nearly as many rolls/sheets per 5 liter package using one-shot development as I will using replenishment. In addition, Kodak's datasheet says that 1+1 gives slightly higher film speed.
