I was just thinking about this the other day. In my local supermarket, I can buy a 20-pound sack of rice for $2.99, at least as long as the current sale lasts. Regular price seems to be about five bucks.
Only if you buy that fancy Evian shit. A gallon of spring water at Price Chopper would cost me less than $1, if I chose to buy it.
ETA: Still a lot more expensive than from the tap, though, which is good enough for me.
This reminds me of the Simpsons episode where several floatillas of boats are in the South Pole cutting and loading large chunks of ice and shipping it back to the U.S. and to the individual stores.
The delivery guy says, “You’ve got to charge more than a dollar for a bag of this stuff, we lost 30 men on the last voyage!”
APU: Hey, if you can think of another way to get ice, then be my guest… 
Movies - Hundreds, if not thousands of people spend months of their lives and millions of dollars to put a movie out, and I can see the end result for around $10 US. A-mazing!
I just synthesized aspirin in Orgo lab yesterday, and it got me thinking about the price of aspirin and other OTC medications. I’m sure the raw materials I used yesterday cost more than bottled aspirin. A couple of dollars will get you a huge bottle. And aspirin is pretty much a wonder drug…pain reliever, fever reducer, anticoagulant (clot prevention). Amazing!
I think that all things electronic are incredibly cheap-compared to 30 years ago. Remember when a basic Apple Computer cost $2500? Or a stereo receiver at $500? You can buy better equipment for much less money today. On the other hand, some things are ridiculously expensive-for example: plastic shutters. I paid $30.00 for two plastic window shutters at Home Depot-they probably contained $0.50 of plastic, and being injection molded, the labor cost to produce these things is close to zero. Or paint-$30.00 for a gallon of paint? The profit must be enormous.
For me, the answer to the OP is… ‘Just about all of them’. This has to be the golden age of cheap, common commodities. Food is cheap. Clean drinking water is cheap. Power and fuel are cheap (even though we often don’t think so). Entertainment is extremely cheap. Computer technology is cheap.
One of the most amazing examples has to be a Skype video phone chat. The other day I was talking to someone in a foreign country, and we could see each other as well as talk, in real time, scarcely any delay. And the call itself was costing us… nothing at all!
A year’s subscription to SDMB.
My iPod.
I remember when the first Walkman came out. People were amazed that you could put in a cassette, 30 minutes on each side, and take it with you wherever you go.
My iPod can store almost 1000 hours of music, for just a few hundred bucks!
Tricity fluid sold separately.
If you watch The Colbert Report, Stephen occasionally marvels at how cheap you can get tube socks.
Napier: Really? If they’re only $55, I might run out and buy one right now. Any chance that’s a typo?
I seem to recall a thread not too long ago where one Doper admitted to wearing socks once, then throwing them away at the end of the day because they were so cheap. Less than $1/day, IIRC. (Which seems to fit, a package of six socks is usually about $5.)