Surely if they'd just amde them all 3g compatible from the start (and they've obviously designed it that way) it'd cost just the same. You're not telling me that a sim socket, an aerial and some software costs £100!
I used to work for a computer company (I won't mention the name, besides it's pretty much defunct now) that sold IT systems to hospitals, local government, etc.
The mini systems in the 70s and 80s had been built by this company but by the early 90s they were buying Unix boxes and putting their own badges on them along with their software. They'd then run about 100 terminals off the one unix server. Naturally, if you wanted to run 200 or 300 terminals for a particularly large site, you'd need to pay more, so as well as more terminals you'd need a server upgrade. Having paid thousands for the extra terminals, you'd also need to pay for the server upgrade – which in some cases meant an engineer coming round, taking the back off, and flicking a DIP switch. In other words, they bought a load of boxes that were all the same from Motorola or whoever, but then provided a range of 'options' to the customer.