Man, it depends on the tire. Be really careful to compare shipping costs. Some places do the cheapo price & zap you for $120-$130 bucks for shipping. That is $40-$50 too high.
www.tirerack.com has fair prices and decent shipping.
www.summitracing.com has the Kumho KL78's, a good all-around tire, and only charges 8.99/ea to ship, last time I looked.
With MUCHO looking around, I found my best deal at a local place. Most places charge extra to mount/balance tires purchased elsewhere, so you have to know that price in advance to get a true comparison.