I don't know what a Fairphone costs where you live but where I live the Fairphone 5 starts at 550€ and the model with more storage and memory is 629€. That is no where even in the near of three times the price.

There are phones that give you this choice. The Fairphones for example. The back cover is easily removable and you can pop out the battery like in the ol' days. It has an IP55 as far as I know.