There are MANY reasons that materials, as much as labour, would vary. There purpose (eg: is its purpose for fire rating/ bracing/ energy/etc etc), the LOOK (all clients like different visual appearances), the availability (you may want stone but it is only avail at twice the price elsewhere avaiialbe)……..the list goes on and on.

And yes, of course a builder will build as cheaply as possible, with materials that will still allow the construction to pass inspections! That seems kind of logical to me! A builder is in business after all, and thats one way they make a dollar.

It doesnt mean it will reduce quality (neccessarily, but it can), it just means builder is trying to find a way to make a buck. Just like the rest of us with what ever we do.

A good idea if you are questioning the ethics of what a builder is doing, is to go get some independant advice from a consultant that deals in estimating/ surveying/ legals……..what ever your issue is. Good luck.