The depth of the well is a huge factor, generally the deeper the well the harder it is to pump water out of it. There is also the matter of how fast the well w

The depth of the well is a huge factor, generally the deeper the well the harder it is to pump water out of it. There is also the matter of how fast the well will replentish. Shallow wells into unconfined aquifers in regions with plenty of rainfall are probably the best sort of wells. Those sort of wells get replenished every year (climate permitting.) On the other hand with fossil aquifers you're draining a finite amount of water that won't replenish in human timescales, if at all. So in some regions pulling water from wells will be perfectly sustainable and essentially free, while in others it's unsustainable and expensive.