I think the above idea works. If you can afford to buy them what they want then do so, but find a way to make them appreciate the value? I think my most expensive present was part of the cost of a bass guitar for Christmas at 16. I knew it was expensive, and took up weekend work, saving every penny for a year towards it, and my parents paid the rest. I also spent ages ringing around and searching for the model I wanted to make sure we got the best price around. I forget how much we each ended up spending but at the end of the day, I appreciated the value of it and took especially good care of it because of that. I appreciate it's slightly different for such a young child, but the idea of making them work around the home towards it is a good one if it can be enforced.
Other than that I'd say a substantial present is definitely better than something they'll just play with a few times, but then I wonder what counts as substantial these days - I'd say a bike was, but a tablet isn't really. I mean, I'm a tablet user and a bit of a tech geek but even I wouldn't have bothered with one if I hadn't have got it seriously cheap; especially for a younger child, given that my younger cousin has such things, and subsequently his parents never really know what he's doing online.
On the stupid advert note, Apple are the worst - I get e-mails around every possible day - Father's day "give them what they really want - the new iPad", Christmas - "It's the season! give them the new [£1800] macbook with blah blah" - I only once brought an accessory from them - how rich do they think I am?!?