Budget by batch size
For standard prints, the core math is price per image multiplied by the number of photos. The real bill changes when you add higher resolution, manual rotation, file naming, cloud storage, return media, or rushed turnaround.
For slides, negatives, and film reels, do not reuse paper-photo pricing. Treat each media type as its own job.
A fair cost comparison uses the same assumptions across providers: same approximate quantity, same media type, same output quality, same delivery method, and the same return-shipping expectations. Otherwise a low advertised price can lose to add-ons at checkout.