(3) While I see what you’re saying re. the wage scale used to derive spellcasting costs, the way the costs of Divine magic scale seems a bit odd:
2nd level spells cost 4 times as much as 1st level ones,
3rd level spells cost 3.75 times as much as 2nd level ones,
4th level spells cost 2.17 times as much as 3rd level ones,
5th level spells cost 1.53 times as much as 4th level ones.
APM: It’s a product of the funky cleric spell progression. A 5th level cleric has 2 1st and 2 2nd, while a 6th level cleric has 2 1st, 2 2nd, 1 3rd, and 1 4th, and a 7th level cleric has 2 1st, 2 2nd, 2 3rd, 1 4th, and 1 5th.
Mathematically it works out as follows:
5th level cleric:
Monthly wage: 582gp
Billable rate: 81gp per day
Highest level spell: 2
Spells of that level per day: 2
Cost per Spell: 40.5gp (smoothed to 40gp per ease)
6th level cleric:
Monthly wage 1,171gp
Billable rate: 162gp per day
Highest level spell: 3 and 4
Spells of that level per day: 1
Cost per Spell: 162gp (smoothed to 150gp for ease) for 3rd
7th level cleric:
Monthly wage: 2,327gp
Billable Rate: 322gp
Highest level spell: 4 and 5
Spells of that level per day: 1
Cost per Spell: 322gp (smoothed to 325gp for ease) for 4th; 322gp (increased to 500gp to reflect that some might be cast by 8th level casters) for 5th
8th level cleric:
Monthly wage: 4,665gp
Billable rate: 644gp
Highest level spell: 5
Spells of that level per day: 1
Cost per spell: 644gp (reduced to 500gp to reflect that some might be cast by less-expensive 7th level casters
So the costs are more-or-less correct. In order to give it a smoother progression I created separate prices for 3rd and 4th level spells and then bumped up the cost of 5th level spells a bit. On the “supply side” 3rd/4th are the same to a 6th level caster and 4th/5th are the same to a 7th level caster, but the game works better with the slight adjustments I made.