I got 110 bonecraft early on
got bc escu in 2019
as far as bonecraft goes and i'm sure it's the same for most other crafts
the only thing holding back more gil accumulation is the fact the top gil synths everyone already has on their main
any sell is going to alts or new characters
as far as numbers I can spend about 30m on mats farming some of them myself and usually make around 80-115m in that crafting session of sellables
now the selling part like is said is what's so slow
I only sell a piece of gear about every 3 days this usually sells for 12-15m
there's a few other things that sell for a little more like aurg orb +1 but that have a 100$ loss on wyrm ash if a break so it's not too difficult to lose it's more like gambling not a sure fire way to make gil
to note su5 synths I've to date never made a neck +2 or weapon su5 with necks going for 40m and weapons even at 130m it's almost a guaranteed loss if you take the normal number of synth attempts to make the weapon
asura things sell faster than odin and for a long time you had the pvp community which needed low lvl gear for fov augs and was willing to pay high gil to get them and wanted a lot
like zeal cap +1 or behemoth ring +1
Eremites ring +1 is my go to synth. on asura it's around 700k. on odin it's still 100k. I really like the synth. farming hermits rings is fun then it's just a sheep tooth. people usually want two. it's a ring that can be used until 75+ from lvl 10
before everyone had so much of the gear or when the gear was the best there was many more options now it's just sticking to what doesn't take 3+ weeks to sell on ah
i'm sure that's the same for most crafts
to add a personal thing i've seen overtime
gold and smithing can make the most but mats more expensive so imo it's decent
leather cloth woodworking all a little cheaper on mats but the sell price is a little lower decent
alchemy and cooking really good for personal use but not many options to make good gil
bonecraft was my favorite from the beginning for this reason cheap mats high sell price really good
I also like that bonecraft can work with fishing catches and chocobo digs specially if chocobo is equipped with bore
the thing about bonecraft for the longest time was one max lvl bc could buy the entire ah out and stop all others from lvling up or crafting to make gil
this is sorta true but stock comes in a lot faster so it's more an issue if someone max lvl wants to ruin the market by undercutting like it was done for so long by escu rmts
now the market is usually 3 or 4 people with escu and they all want the most gil they can get per synth so they all work together
long post didn't expect to explain this much
hope it helps even if just a little