I put three layers of cheap underpad and a layer of carpet on the floor; you really didn't need a bed, it was so soft. 63 holds, six sheets of plywood and a pile of 2x4s cost less than an iPad and lasted a whole lot longer.
The wall got a lot of use over the years, and was known as the coolest kids' bedroom around. When I put it up for sale at the Mountain Equipment Coop members resale website for the price of the holds, I was surprised to find that it sold for my asking price in about half an hour, and that I got a dozen emails over the next two weeks that the ad stayed up. ( I clearly sold it too cheap but it found a very good home).
Here is something that took two weekends to build. Since it was designed for disassembly we were able to take it apart in six hours and give someone else the opportunity to use it without a bit of waste. It provided a decade of fun and exercise, something we could do together, although I found it frustrating that I could never make it across the top and down the other side like Hugh could.
It certainly was a better investment than any of the electronics I ever bought the kids.