Well, Flight Attendants' salaries can really vary, depending on the carrier. In my first year with United (1996), I made just --under-- $20,000: not much for a struggling San Franciscan, I'll tell ya! However, new hires at United (last hires were in early 2001) will probably take home more these days, but not much more. I'd say they'd be very lucky to come close to $25,000... at any carrier!
After passing the five-year mark with United, I graduated from the lowly "B-scale" salary level, which saw me earn about $1,000 more per year through those first five years. United's sixth-year "A-scalers" jump to roughly $30,000-$35,000, depending on how many extra hours you put in, and whether you fly domestic or higher-paid international routes. You slowly increase to, perhaps, somewhere between $45,000 and $50,000 once you reach your 14th year, where our salary scale increases stop.
There are plenty of ways to "sweeten the pot" still more, though. Speaking a second language and regularly flying as a translator could earn you around $1,500-$2,000 more per year, I suppose. Also, at United we do earn a small commission from duty free sales on international runs. I know one "senior-mama" flight attendant who never misses a chance to push those duty free cigarettes and liquor bottles, and she brings home a tidy little sum (almost $2,000) at the end of the year. The best way to increase one's paycheck is to become a dedicated Purser on our widebody international flights. Expect between $5,000 and $7,000 more per year if you routinely fly as the crew's leader.
The first five years can be very difficult for Flight Attendants at major U.S. carriers. You're on reserve status for much of that time, which means your paycheck can vary month-to-month, you may be forced to readjust to new living arrangements far away from your hometown, and bills certainly do have a way of "popping up" as you embark on a new career and lifestyle. Flight Attendants of smaller U.S. carriers earn even less when starting out, and I doubt they could even come close to the salary level of a senior international flyer at a U.S. major. Certainly, the road can be tough at first, but I do feel it's a road worth travelling!
Bear in mind that my salary figures are truly rough estimates for United crew only, though. I rarely work up to my maximum allowed number of flight hours per month, I loathe working long-haul international runs (even though I miss out on significantly more pay), and I run away from the Purser role.
...Hopefully a more money-minded coworker will give you more accurate figures. I hope this info helps!