I have basic pricing info from SP and it's not too bad if we can get enough people. Basically, the first key each is $150 and after that they reduce in price significantly. So going with what you said for simplicity sake, let's say black keys with what "text." Here is the breakdown, not including shipping (no idea how that works in a GB)
price for 1 person: $1,721
price for 5 people: $348
price for 10 people: $177
price for 15 people: $119
price for 25 people: $74
price for 50 people: $38
If more than a handful of people express interest I'll try to figure out shipping and get numbers that are %100 accurate, but I think we can all agree that unless at the very least 10 people are in this is too crazy.
Honestly, you'll need to be in the 50 person range to spark a lot of interest, I predict. A lot, if not all, of the full-set (104 keys) group buys are less than $100. For this set, $177 puts it at ~$15 for a single key. That's a bit crazy to be honest.
What I would suggest (I'm no expert) is to simply list the set at $38 with a MOQ of 50. Gather interest and perhaps go ahead with the buy, but this way people will be more likely to sign up knowing that the most they'll be charged is $38. With the tiered GBs it's a bit of a gamble, but much more reasonable since the molds don't need to be made, so the highest tiers are still do-able. Anyway, given the nature of this set you're trying to get made, I think it'd be best to do an "all or nothing" GB and set an MOQ of 50. My 2 cents.
Oh, and at $38 for the set, I'm interested.