Ironically, it is still bad business in the US even to have common non .com extensions. People often can only remember .coms and if your advertising a non .com you have to emphasize the extension in advertising.
However, if you have a website that your not intending to make money from, then risking a non .com extension might be possible. Possibly over time people will catch on to a non .com extension, but sometimes people are greedy for website profit, and therefore want the .coms, hence why certain ones are so expensive.