It's a 'small' issue

The Kiddo is almost five years old. I have to shake my head, seriously, in three months he will be 5!! Where did the time go? He is so small that quite often I forget that he's as old as he is... but one of these days real soon he'll probably start growing. Which brings me to my issue. Why the heck are beds so darn expensive?! The Kiddo has been sleeping in his crib since he was just about a year old.
Several years ago we took the side slats off but it's still a crib sized mattress in a crib sized space.
Either the bed is getting a little small or the kiddo is getting a little big. See the Kiddo doesn't sleep to well a lot of nights and my theory is that, because he is an active sleeper, when he rolls over he hits the side or bottom rails and wakes himself up. So the Man and I talked, and talked, and decided that he might just need a new bigger bed. So we went and asked the Mans mom if we could have back the full sized bed she gave us two years ago (we returned it when we moved into the apartment hoping to save space for awhile). She told us we could not have it again. So then I did pricing on beds and realized that in order to buy him one we'd have to pretty much sell the car! I guess he'll be struggling to sleep in a small bed for a little while longer.