There are a variety of ways to price things.
Professional Photographers of America publishes much current info, mostly for portrait and wedding studios but a reasonable guide.
Typically prices are determined by a ratio related to "cost of goods sold" (COGS) based on what successful studios do. For film based work 30% COGS is normal. (For digital studios, 20% is a normal COGS number, digital doesn't really cost less, depreciation is 10% greater.)
So, if the cost of your labor and materials for production is $30 a sales price of $100 is normal.
So for a sitting/session with proofs it will cost me about $30 per roll; film, postage, developing, proofs, and scans. So my rate is $100/roll that I shoot.
Prints, same basic deal. Labor plus materials is 30% of the sales price regardless of print size.
My labor costs (for pricing) are based on market rates for the work involved. For me that means simply "what it would cost me to hire the same work done at a high quality lab". Doesn't matter if I'm personally slower or faster doing the same work.