From the pictures on the PFU and Topre sites, it looks like the capacitive part is only responsible for the electrical signal, whereas the tactile feedback is due to the sping. Cherry G81 keyboards use rubber domes, but the key return is provided by a spring. I guess you can call them "half-mechanical". They are fairly cheap. A G81-3000 should be around U$40-50. Has anyone tried one?
EDIT: BTW, G81 is specified as linear feel.