They are prizes that are awarded in promotional contests in support of the name of the product on the grill. Here's how it works: They display the "logo grill" in a store or some other public place and entice you to fill out an entry form for a chance to win said grill. On the entry form, you supply your name, address, email address, and phone number. This is what they really want. The idea is to harvest as many legitimate names and addresses so they can in turn sell this "valuable" information to retail marketing firms many times over. These retail marketing firms put you on mailing lists, call lists, etc. and bug the hell out of you.
So for the paltry cost of a basic Weber grill, they get in return, a valuable mailing list that they can sell and resell for thousands of dollars many times over to many different companies. You didn't really think that their motive was to give you a Weber grill, did you?