Matias makes full-sized keyboards with mechanical switches that are much less expensive than the half-keyboards. They are priced from $130 to $150 or so. The half-keyboards are niche products and they are more expensive in part due to the tooling costs being a much more significant proportion of the overall cost of manufacture.
There are quite a few mechanical keyboards available on the market that are cheaper than Matias, and some that are more expensive. Unicomp has has both Mac and Windows layout keyboards for a bit less than the Matias boards. There are also a large number of offerings from various manufactures that use Cherry MX switches. The cheapest that I am aware of is the Monoprice Mechanical Gaming Keyboard with Cherry MX Blue switches, which is about $60. It's acceptable, but the Matias boards have a much higher standard of build quality.