Database design for a group-buying site
This is an idea I came up with that can help (see attached image).

The Deals table is simple. It has an ID that defines the details of a deal (like product name, origin, etc). That info through the ID is passed onto a deal_instance table thats designed to setup the individual sales to that deal. This is where your "K" comes in.

Then I added a customer deals table because any number of customers can buy any number of deals and vice versa, but in the customer deals table, the number bought is recorded so you know which customer bought which deal and how many times.

Then you use that information to find out when n people bought the deal and how many times. Once that value is met, then you go on and create another instance for the same deal just by adding another record to the deal_instance table using the same deal ID. If I'm not mistaken, the left most line needs to be an arrow, not a slash. (1 to many relationship).