We're talking about apples and oranges here. The couple SSMGuy is citing likely consist of a dominant and a submissive. There are many submissives whose fetish includes being ordered to do completely non-sexual things--household cleaning, chores, cooking . . . There's a blogger named Holly at http://pervocracy.blogspot.com who just yesterday posted her "BDSM Checklist," and discussed some of her ambivalence about that kind of submission. She's submissive, and she likes being told what to do, being forced to do it, and even enjoys the kind of chore-doing stuff being discussed here. However, she's not married--she's "playing" with boyfriends, friends, and sometimes strangers. She also discussed the question of when this crosses the line from her having her fetish fulfilled to her serving as some guy's free maid service.
Either way, if you're not the kind of submissive who has the very specific fetish that allows you to take sexual pleasure in scrubbing someone's floor for him/her, then I don't think it's very controversial to say that it's a bad idea to barter for sex with your wife. Apples and oranges again. And it gets worse when, as is often the case, one spouse is trying to barter for sex without telling the other (the "hidden bargains" or "unspoken deals" that Glover describes in No More Mr. Nice Guy, where the husband might do anything from going to a bad movie to washing his wife's car or the dishes, but then expect her to reciprocate in some way, often sexually. It seems like he's doing something nice, but he didn't do it to be nice, and since he didn't actually make a bargain with his wife, she won't feel obligated to "keep the bargain" or even find out that she was supposed to do something. It's self-defeating.)
