You guys fail to understand the revenue they generate by a little "gimmick" like this (or their hopes of, at least).
A Boxter is worth only about ~ $50,000 (off the top of my head).
In hopes of you entering their sweepstakes, they estimate a certain percentage will actually read the rest of the spam mail, visit their site, and buy something. Think of the Boxter or $50,000 as an advertising/investment cost, which is relatively on the low side.
(and $50,000 to a company is pocket change nowadays...
if they advertise it, they can afford it)