Every time I go to a pet supply store, I am absolutely amazed at the prices. The price for something simple like a cushion for a dog cage is about twice the price of a similar item meant for people in a regular store (i.e Walmart, Target, etc).
For example, when we first picked up our dog, Keena, from the shelter and took her home, we wanted to put a pad in her cage as we were crate training her.
For something like $30, we purchased a foam (not a memory foam, but a cheap foam) mat with a vinyl cover from the local Pet Smart. Because the vinyl cover had a zipper and seams, Keena would get curious and pick at the zipper and seams when she would get bored during times in her cage. Within days, she had completely torn apart her bedding and we were out a quick $30.
For a while, she went without a pad, as we didn't feel like blowing another $30 that quickly.
But then one day, we were at Wal-Mart or Bed Bath and Beyond (I don't remember exactly which). We were in the bath section and I saw a memory foam bathroom mat for $15.
We bought it, brought it home, and were amazed to find it fit PERFECTLY in her cage .
Since there are no seams, Keena hasn't torn it up and she's been sleeping comfortably on it ever since. Because its memory foam, she hasn't warn it out and its still as cushy as the day we purchased it over two years ago. Plus, since its a bath mat, it is washable so we can just throw it in the washing machine to clean it.