Assuming that this special set would cost more than the regular sets that is currently selling at EK for $110, tsangan's estimate is totally reasonable. Like I said, since EK said, "oh, you guys are not going to have enough orders to trouble us", find out from EK what the minimum number of sets MOQ) is to make it worth their while, and approximately at how much per set. Without this information, we can't move forward.
This is just like a keycap group buy with SP, except SP is able to give us a price list whether they think we can make their MOQ or not. Whereas EK doesn't seem to care, or maybe they just don't have the capacity (not enough time or human resource) or ability (not able ask for special order or it is just too much trouble to worth their while) to do it.