37signals made a bad decision with this, in my opinion. They don't emphasize the expensive packages first, to make the cheaper packages seem more affordable. They make the one you want huge, and the 49 dollar price, at first glance, seems expensive. If they emphasized or drew your eye to the $149 package first, by the time you get to the package you want, at 1/3rd the cost you were looking at before, you'd be more inclined to feel it is a good deal.
Look at WuFoo's design, they do an incredibly great job at the price chart, and they can back up their decisions with data.
On the other hand, if your service is not something you're trying to upsell people on based on gimmicky features, I strongly suggest following the Slicehost model: http://www.slicehost.com/ They know you know what you need, so they very plainly list all of the plans and their prices with no gimmicky sales bullshit. I love them for that.