How do you forecast what an AI feature will actually cost — before you build it?

Weaviate pricing to check: Vector Database Pricing | Weaviate Powering recommendation engine per user history on Beat of Hawaii (the recommended posts https://beatofhawaii.com ) - 5k posts, embedding 1024 dimensions, around 2M unique visitors per month… Originally we were around 75 USD/month, but recently they updated pricing and offer, so we fell to 45 USD/month. 3 years+ of operations, no issues so far.