I'm not too deep into fantasy economics, as it immediately ties into a lot of other price dynamics. I find that Brave has a very strong list of goods and services, and I feel like that would be a pretty good guideline (though maybe training should be a bit more expensive than that).
I think the cost of training should not just be gold - there's a lot of fun to be had in finding and convincing trainers, before gold even enters the picture.
Appendix B goes into making NPCs (and monsters). My general usage of it comes down to:
- NPCs and monsters are always damage proficient.
- Notable skilled combatants might be weapon proficient. This makes it A) easier to run as a Warden, and B) reinforces the danger of these combatants.
- Notable skilled or dangerous combatants might have the ability to fight back, block, dodge or parry - see Appendix B for suggestions.