I found that when I looked for a TV 2 years ago that you couldn't just assume a price would get you the unit. Some had none in stock and would advertise them and if you ordered wait to get like 50 orders and than order, and it would take months. This happened to a friend that actually did it. I also found prices below dealer cost, which for a non dealer is a red flag. I got through that on a Krell non dealer and called and said I would take one only if it shipped tomorrow and I got it within 3 days, and than the truth came out.
If you get one of the bigger one's that won't happen, but the prices are also not as good as some of those with such restraints. So the real deal is just because on net, doesn't mean you can get either timely or without a very large shipping.
I will buy components, but with TV, found that you don't pay tax, but pay around 300 for shipping which makes it a few hundred to 500 if you negotiate at the store, and obviously if a problem it is tough and long, and you don't get the 30 day return thing. I concluded for TV's at the high end not worth it, but for components no problem. The last thing you can risk is B-stock items which with some manufacturer's is hard to get out of them, and you can get answers like you are assured with a dealer that it is not.
It will all change with internet tax coming up, which I hate because in some case it has kept retailers fair, but I do see in others that the local dealer shouldn't lose business because of tax. I did find one thing with highend that was odd, in the sense that dealers get cost breaks like with the Pioneer Elite dropping a grand, but non dealers are stuck at the higher cost basis, so if buy in one of those times, you can actually lose money because of non dealer not getting applied to existing inventory. This happens when it occurres after you did all your price shopping, but before you pull the trigger.
That was a very good question, and as you can see I looked into this alot for different things, some with luck others without, but I tried to cover the major factors that I ran into, and I am sure there are one's that I didn't experience but exist. I recently got a TV wholesale but local that had problems and had I gone retail it would have just been swapped but for that 600 I saved, because it was bad, I went through hell. Had I gotten that 3rd party and not local, I would have lost much more money, where now I am just out 200 for the extra pickup/delivery, and 3 months of my time.