Plus it isn't trivial to get 3 levels of a specific proficiency.
I disagree.
- "Civilian" characters get four free proficiency ranks at level 0 in lieu of Adventuring proficiency.
- Alchemy is a general proficiency. Any PC with Intelligence 16 or better starts with 3 general proficiency ranks at level 1.
- The Alchemist specialist has Alchemy 3 by definition. There's at least one for hire per month in any Class III or larger market. Their wages are 250gp/month, sure, but with the average Fighter collecting 1600gp by the time he makes level 2 (assuming 80% of XP from treasure), 250/month isn't really cost-prohibitive.