A staple of high-level characters in D&D is boosting their abilities with inherent bonuses; up to +5 for each ability.
There are essential two methods of obtaining those bonuses:
- The Manuals and Tomes; a Manual of Bodily Health +5 costs 137,500 gp.
- Wish spells cast in immediate succession; 5 Wish spells in immediate succession cost 25k XP to the caster1.
There are various dubious methods which can be found on the Internet, such as using distilled joy or liquid pain to offset the XP cost or conjuring Effreti and milking them off their Wishes. Such methods generally rely on a push-over of a Dungeon Master2.
Baring a push-over of a Dungeon Master, what is the cheapest way of gaining Inherent bonuses?
1 Hiring a spellcaster to cast Wish costs
26,530 gp = 17 (CL) * 90 gp (9th-level) + 5 gp/XP * 5,000 XP, for a total of 132,650 gp for +5; though as per the rules of goods and services even a metropolis is not guaranteed to have a spellcaster able to cast 9th-level spells. Also, it seems that a spellcaster with 25k leftover XP, and thus a 25+ level spellcaster dabling with Epic spells, is unlikely to be moved much by a mere offer of 130k gp.
2 Where push-over is defined as giving an advantage to PCs that its own NPCs are denied. For example, if the PCs use Effreti to get free Wishes, then there should be no reason that affluent NPCs would not also use Effreti to get free Wishes. Or if Liquid Pain is on the table, then clearly Evil NPCs would use Liquid Pain to achieve their objectives, ... As a result, answers should attempt to limit DM's intervention as much as possible, knowing that anything the DM allows for the PC may be allowed for their foes going forward (if the DM doesn't outright refuse).