At our housewarming party, our friend gave us a beautiful set of tall and short drinking glasses. We absolutely love them. However, it is inevitable that glasses will occasionally be broken. When I broke a short one, I was upset and dismayed that eventually enough of the glasses would be broken that we'd either have to get rid of the set or have mismatched glasses. Then one day at a thrift store, I found a glass that matched the set. It cost $.59. I scooped it up, happy to have a full set again.
Now, every time I'm at a thrift store, I scan the glasses for both tall and short glasses in our set. It is a fairly common design, so I've been able to scoop up several. We now have extras and when the occasional glass breaks, it's no big deal. I pay between $.25 and $.90 per glass. This is cheaper than the cost to buy a new set.
While for certain sets, it may be a long shot to find replacements, it is definitely worth a quick scan when you are at thrift stores or yard sales. You just may find a cheap fill-in to stretch your set.