By minimum order I just mean the volume at which I calculated the prices in the OP. It's nothing that SP is enforcing. So if we didn't make it to 75 REDESC and 40 RGBY, then the prices would have gone up or we would have had to scrap the buy (or maybe just the RGBY sets).
The base key breakdowns I'm working from are posted in the interest check thread. These don't include the legend setup fees, the shipping cost from SP, Paypal seller fees, etc., all of which are baked into the final prices.