A: Fair Question :) We see the on-going prices at eBay is well over $100 these days and this is only our theory so please take it with a pinch of salt.
The item is well-made with lots of sounds and LED lighting effect, good design (probably better than DX Driver Driver). Since Drive Driver failed to be popular with the concepts to have 2 devices for one on your belt, and the other on your wrist. No wonder the simple Mach Driver has became more popular to the Drive Driver after the show ended.
Popular one will come with higher values. That is how the market works and is why we brought our used toys to our store. Although we hunt for the pre-owned DX Mach Drivers, their market prices are still steep and naturally it effects our prices as well.
Why it is so popular and in high demand? The simplest answer is because there are people who love this product, just like you ;D
That is why it is worth to have it.