Speaking from some experience:
WWF (I don't call that shit WWE) don't pay rasslers shit. WCW was a good paying company, scrubs would make at least $100K. I can't speak for TNA, but seeing as they make nothing from house shows, and do a PPV a month, they probably don't pay well either.
For the WWF, if you're not moving merchandise, you're not getting a good contract. Back in the day, cats like Stone Cold, Triple H, The Rock were able to get million-dollar contracts because their appearance would mean increased ticket sales, PPV sales, and merchandise sales.
Most of your average cats now (exluding the biggest names) are probably clearing $60-75 a year, working 6 days a week, all for the "opportunity" to make their name bigger. Hotels, transportation and meals for a gig that keeps you on the road 49 weeks a year...