I'm not sure what the demand is, but the G13 itself retailed for only about 70€/$80 new when it first released in 2004. The razer Tartarus should be about the same price.I googled a few of the products you mentioned, which is an area we've never covered.
Is there a high demand for these products at the moment? I saw the price of Logitech G13 is $450, very high price.
Looks like the G13 got discontinued recently and thus scalpers are trying to scam people, $450 is definitely ridiculous for that chunk of plastic and rubber dome keyboard, no matter how neat I think it is.
For something with mechanical switches I'd probably shell out about 100, maybe more if it's hot swappable. The display usually felt like a pointless gimmick so that could easily be cut, almost no games utilized it in any way that would make it worth looking away from the monitor.