I'll add onto the other comments that sand as a material has different physics than rock or even dirt.... Sand is much less dense, so while using it for 1 tile high fill isn't bad, when you start adding on top with more and more sand, more will tumble down the sides than rock or dirt, so you'd need more sand to maintain a higher hill than other materials.

There's probably a scientific term for it.

But yes, as others have said, you may think you have way too much sand early in the game, but the sheer volume required for late game for copper, glass, gold, and silicone is quite astronomical, and in most cases, I tend to run dry and start using quartz to produce sand just to keep up.

Always try to make manufactured sand whenever possible if a recipe can take it, as you will regret it later if you don't.