And in addition to the cost of the chemicals, I would also need to buy a scale that can accurately weigh 0.1g, right?
My concern with mixing up developer at home is not so much the initial cost, or the difficulty, but I wonder about stability of the necessary chemicals? I assume, if any one ingredient goes bad, the mixed developer will not work as expected?
I may try mixing my own developer one day, but there are several interesting commercially made developers I'd like to try first. I suspect factory-made developers are more precisely controlled for consistancy of results than what I could manage in my basement (but after getting burned on a bad batch of Kodak Xtol, maybe not?)
However, there may be a few diy formulas that produce results which are noticeably different from what can be obtained from any commercially prepared product, and therefore may be worth the effort. Is Acutol S / Crawley's FX-15 developer is one of those?