... you wil be hard pressed to out do a 3-5gig cap on just browsing and some email.
Higher caps are really only for downloading, hardly browsing, you cant really use just browsing as an excuse for much higher cap than say 5 gigs.
Depending on your interests, it is hard to exceed a 3Gb cap, but the quoted 200Mb - 500Mb (from the article) is a heck of a lot less than 3Gb and can very quickly be used up unless used ONLY for e-mailing (without a lot of large attachments) and general surfing. The moment you start using the Internet for more (such as keeping Windows Update(d), ensuring you have the latest Graphics Card / Sound Card Drivers, doing Academic / Business Research - with multimedia downloads of pictures, movie clips, affiliated stats etc.) 3Gb may not be enough unless your scope / interest is limited.
For example, with all the hype for the XBox 360 launch, I've done some online research and browsing the tomes of info on the Internet, you'll quickly find high-resolution screenshots, streamed interviews and downloadable trailers for current and upcoming games. I assure you, using up 100Mb over a weekend checking all the related sites is very feasible - I've done it. With Sentech's 1 'cheap option' this is a 50% utilisation which leaves very little for the rest of the month.
It gets a lot worse if you're a gamer. For some nostalgic reason I decided to give EQ a try last month. I downloaded the EtN trial and subsequently bought the Platinum Pack as well. Patching the core game and expansions for EQ alone cost just shy of 2.8Gb of bandwidth last month. Then there was the nearly 600Mb Guild Wars World Preview Event for the upcoming NightFall Expansion. These were over and above the normal, scheduled maintenance patches for GW and CoH/CoV. Needless to say that for the 1st time ever, I exceeded my monthly 4Gb cap by an extra 2Gb in September. EDIT: Almost forgot to include the Patch for WoW

... I luv games and switch from one to another when I get bored - luckily they each offer something unique, hehe
If I didn't play online games, I would've been below 3Gb, but without the Patching it is impossible to load the games so I had no choice at all. Someone with interest in fewer games than myself could still manage with 3Gb IMO but my point is that the Internet should not be limited by factors of cost or bandwidth availability - with sufficient planning it does not have to be a 'limited' resource because it's artificially created. We don't harvest bandwidth, we don't mine bandwidth, we don't eat or drink bandwidth - we using connected hardware and software to create it. This makes it a renewable resource and should thus be priced a lot cheaper.
But I've digressed. The bottomline is that the article highlight's Sentech's shortsightedness in their product offering (at least to me).