i dont have compleet details but the "link cable" is as far as i can tell a universal 4 pin (about 3/4 bucks for a short cable)
the modules realy depend on what they are, if u want a feel of price u may wanna check out
sparkfun they may have some that can be already compatible
just to give an example if we make an gps module it be in the €60 to €80 range
wile the IR transiver or the ghost thing is like next to nothing
the thing about hardware is the bigger the production the cheaper the device gets
so the final price depends on the first batch and how much the indiegogo makes