There are some knock-off Topres that are less expensive. For example, Royal Kludge had some boards that showed up on Drop a while back. I haven't used them, though, and they don't seem to have really caught on.

I had a CM Novatouch for a while, which was Topre-based. It wasn't my cup of tea (I'm partial to dampened ALPs switches from old Apple Extended Keyboards), and I eventually sold it, but it was a solid keyboard.