"Wow I have gone through hundreds and paid millions.
What is draft of the craftsman?
Available from the in-game store, Draft (actually may be spelled Draught) of the Craftsman lasts 2 hours, and causes every failed tradeskill combine to return ALL mats, so you can keep combining over and over til you are successful.
The key here is, you can skill up on both successes and failures, though you have a better chance on successes. For both successes and failures, the higher your stats, the more likely to get a skillup. So, for higher level players with stats in the 1000+ range, you just want to be making as many combines as possible. The minimum success chance is 5%, so 1 in 20 (on average) will succeed, but you'll have a chance to skillup for every combine. By getting a guaranteed salvage for all mats, you want to fail a lot, and just keep combining.
So, you want to minimize successes, which means, no mastery AAs, and no trophy.
The DotC costs 1750 DBC, minus 10% if you're all-access. You can use the calculator on EQTraders to see when your combines start to go past 5% success rate. When you hit that point, then move to a higher combine.
Tatanka Wolfdancer, 106 Wood Elf Druid, 7 x 300+ Master Artisan, 7 maxed trophies :)
Anaceup Mysleeves, 105 Erudite Mage, 2 x 300 Master Artisan
Snookims Whinslow, 105 Erudite Enchanter, 2 x 300 Master Artisan
<Inisfree>, Tunare (Seventh Hammer!)
Tatankaa (95 Inquis)/Urkell (38 Conj)/ Seanthornton (24 Pally), <Inisfree> Freeport server (some other server now)