Which retailers even have these?
I'm thinking that if they're being sold for $30, then that means the demand for them is high enough. In fact, if these are selling easily at $30, don't be surprised to see other retailers set their prices well above that required minimum mark.
Yes, Discraft can only ask retailers to honor this. But, Discraft can also choose to not do business with others in the future. More likely is that if a retailer does not honor their request, they will decide not to give them a future "limited edition" item.
Manufacturers can set minimums. Innova actually has a minimum pricing on all of their products. Ultimately this prevents retailers from having low-price battles which decrease the value of a product. Keeping value high is good for retailers who need profit margins to stay in business.