Need Help with Archetype Ability

So I'm trying to create an archetype for the alchemist that gives up mutagens, bombs, or extracts (player's choice). In exchange it can create magic items with a specific GP value for each level. At 1st level this is 250 gold. At 2nd level it's 500. From that point on, it's 1/3 of the Expected Wealth by Level.

Is there an easy way to set this up?

My hope would be a single script that can do this. If not, I don't mind having to do 20 class abilities but I would like each one to override the previous so that it only printed the current GP value they can have.

I would also like to know if there is a way to set up the archetype so that the player chooses which ability to give up. I don't mind having 3 separate archetypes but a single one would be much more manageable.

3 different archetypes - the user makes the choice when choosing which of the archetypes to use.

That's what I was thinking I would have to do.

What about the first question? Is there a way to have an ability that is tied to Wealth By Level?

My current plan, if I can't tie the ability to the Wealth by Level is to have it just list the ability at each level with a specific GP value. I tried to create a class ability that I was hoping I could just use to override a previous ability. When I select Append Reference for the ability I want it to replace, I still end up with both versions. I would like to have this be the same ability that improves every level.