When you're starting a collection of movies in Blu-ray format a few bucks saved on each title definitely adds up to a significant amount of money.
If I had paid $29.96 + tax for my copy of Iron Man that would have been nearly $7 above what Amazon charged ($25.95 and no sales tax & free shipping).
I saved even more ordering The Godfather online. It was $61 at Amazon. The lowest local retail price was nearly $70 plus sales tax (bringing the total over $75).
Earlier in September, I ordered the Kill Bill movies from Amazon for $20 each. Local retailers were wanting nearly $30 each. So instead of paying $60 plus tax I spent $40 instead.
Over the past month I've saved close to $40 on four different Blu-ray releases by getting them online versus paying for "instant gratification" via retail.
During the early years of the DVD format prices on movie discs were pretty high, so I ordered online quite a bit more often. I started buying from retail stores more often when movie studios started getting aggressive in their pricing strategies (like pricing The Matrix DVD under $15 when it was first released).
Amazon is definitely the easiest way to guarantee a good price, but they can be found at retail, too, if you do a little shopping.
Kill Bill could be found a few weeks ago at Fry's (which I realize everyone doesn't have) for something like $26 or $27 minus $10 if you bought both together, plus they had a $10 per movie rebate from the studio...for a total of like $12 or $13 per movie. Wal-Mart.com had them for $23 also, and BB would price match that (I know, I did it), and I still used the $10 rebate which, by the way, the Amazon copies didn't have. So I'm actually getting mine cheaper than I would have from Amazon.
Same thing for the Godfather - BB.com and Wal-Mart.com both had it for $61.95 the first week it was out, and even if you couldn't find it for that at BB, again, you could take a walmart.com printout in there and get BB to price-match. Yes, you'd still pay sales tax, but still...
And don't forget, many websites will sell cheaper than their B&M counterparts, but most of them offer some version of in-store pickup, where you can still have it in your hands the same day.
It is a little more work, I admit, but I always prefer to walk in and pick something up as opposed to waiting for it to be delivered.