You need a leather sefer bound or a standard sefer bound?
For a standard book or sefer it's worth having it bound if it's still in shape meaning pages are all not loose, it's fine if all the pages came out of the actual cover, but when you have one page over here and another page over here that actually came out of the bound pages that makes it a bit more complicated.
It shouldn't cost you more than 5-$6 per sefer.
Back in the day I bound hundred's if not thousands of sefarim, if it's bound right you can get good life out of the sefer.
No need to buy a new one when you can bind it.
Like meantioned find a bachur in a yeshivah and have the guy who binds for the yeshivah to do it for you. Should be max $5-6 like meantioned before.