There's no such rules, sorry. For rituals, you could probably copy 3.x's rules (since it's costs are fairly similar), just add the material component cost as well, as the cost for services rendered.
Spells cost hardly anything, but maybe the 5 minute rest time. (NPCs virtually never have daily abilities.) Having said that, there's little call for hiring such spells. You'd usually hire a ritual-like spell in 3.x rather than pay a wizard to cast a single Fireball. Even a spell like Stoneskin (which is a daily spell) only lasts 5 minutes, putting a severe limit on buying one, even if you let NPCs cast it in the same way PCs do.