I work in the outdoor equipment industry, and I've been selling tents for years. When you look at two different tents, and one is $200 and the other is $400, there's a good chance that there's no quantifiable difference between the two. Tents have different features that will randomly affect the price. A $40 tent will probably just suck. Fiberglass poles, cheap fabric, and shoddy design will add up to a heavy, bulky tent that's hard to pitch. However, a $600 tent isn't going to save you from nuclear fallout, it's still just a nylon bubble held up by some poles.

As with anything you spend a couple hundred dollars on, the main thing you should approach a retailer with is a list of things you want. The tent with really great stitching, a giant vestibule, and packs down to the size of a churro may end up costing less(or more) than the one with a great footprint, double doors, and poles made of recycled space shuttles. If you ask a clerk which tent is the "best" he'll usually show you his personal favorite, or the one his manager told him he needs to move 60 of in the next week or they(along with him) will end up in the yard sale.

If you don't know what you want out of a tent, buy the cheapest tent in the "backpacking" category and you'll probably be happier than a clam.