I don't agree with this statement. It depends on your region, and sign-ons in the phx metro area are in the 15 - 20 K range for 3 -4 year commitments. Their are rumors of even higher here now.
Even at that, I would not take one. You need to remember that you will only get 55% of that after it is taxed, which reduces it to 8.25 - 11K and then you have to stay with them for the entire time or you pay it back, the entire amount pretax. When you break it down, this is only 1- 1.5 months pay for sticking with a place for 3 years even if it sucks, and once you take their money, you lose much negotiating power. You can and usually will be sent to stores out of your control, such as inner city stores here in the metro area, and will become the companies Bit#$ for lack of a better term.
Signons need to be of a much higher amount or less time, such as a year. Selling yourself out for a freaking month and a half of pay is stupid.