First of all, most sales aren't for $0.5M homes. When I bought my house, my buyer's agent's 3% commission came to about $3K.
Second, that fee is gross, and includes all the overhead of running a business. I actually felt a little bad for my realtor: not only did his broker get a big chunk (50%?) off the top, he had to incur all the expenses of driving me around to view dozens of houses, dealing with the seller (who was a little ridiculous, and trying to sell the house before her bankruptcy had been closed out), buying me a fridge to close the deal (the FHA mortgage required a fridge to be included, but the seller didn't realize that and sold it a few days before closing), etc. He earned the $1000 or so he netted for his four months (part time) of work.
Third, the 3%-regardless-of-property-value "rule" is indeed stupid. There are realtors around here advertising on the radio that they'll do the stuff you listed for something like 1% + a fixed $500 fee (not including the buyer's agent's fee, I assume), which makes much more sense as a pricing model.