i have about 370m now, and reforging i usually am pretty lucky on re-rolls there's only been like 1 roll that i didnt get it within 30 rolls, was costing a million a try, but i cant see how people spend 100's of millions...that just is silly, if you dont get it by a few mill a try, give up, not worth the 1% from 5 to 6% for example, imo
Gems cost me a bit but really once you have 5-6 perfect ones for each toon, like 5 reds, you dont need any more for that toon, you get 3 in chest and 2 in pants 280 of x stat, maybe another for helm, and soemtimes you may get a ring or amulet with a socket, but really 5-6 ruby/emerald/topaz per toon is all you need...i have all 6 of my toons with at least 5 perfect gems of their mainstat, and then emeralds you need 1-2 (usually 2) for thier weapons, i did the math one day, i was bored, but basically once you have all the gems, there isnt really anything else you spend gold on
Crafting costs are minimal, you could maybe spend a few million in trying for a perfect roll crafted augs or crimson etc, i could see that...but really if you have 370m like i do, not like you going to run out anytime soon, or ever, with botting i was making 10-20m a day, most i made in a day was like 30m maybe, doesn't take long to build up a nice amount. I dont run ghom though i got really bored/tired of that even if it is the "best" i prefer t4/t3 rift bot or act4 or act1 bounties, those usually have the best results for me, although at paragon 440 now, i only gain a few levels a day, but I'll get there eventually.
Oh and i dont run bot 24/7 so 30m for 12 hours i guess is pretty good on average?