An interesting question. My opinion is that it would depend very much on the exact set of circumstances. eg Need to raise money for a lifesaving operation on your child, I suspect a great many women and men would do things they wouldn't have considered before to save that childs life.

Depending on any couples set of morals it may not be a big deal, if their standard of life could be much improved by it. Will also depend on how confident in their own relationship that they can seperate sex from emotions.

Price
 

I almost set up my ex with a stranger to do some nude photography but he cancelled. This idea was met with a bit of shock and reluctance at first, but when I pressed it, she got really horny. I was going to drop her off and he was going to pay her 250$.
In my single days, I also propositioned a wife to come to Vegas and it looked positive but I had to do a last minute change.
Perhaps I will pump out my wife now one of these days. She will be good for a hot photo shoot and perhaps a handjob. It depends on the price.

$9.99 apparently

Photography
 

One of my had a brief career trying tl make it as an artist. He mostly focused on photography but experimented with other mediums as well. At one point he was taking a painting course and ended up becoming friendly with a woman in her early 40s (he was probably 25). Toward the end of the course he got the balls to ask her if she'd be willing to sit for him as a model; he wanted to paint her nude. She was hesitant at first but was willing to consider it. He told her he'd be willing to pay her for her time. She said she would need to talk to her husband. She came back the next class and told him she would. That next weekend, she went to his studio space and stripped down completely and let him paint her (in a tasteful way). He showed me the painting as well as a couple photos she let him take of her. She looked great. I always found it really hot that this married woman who had never posed nude before, agreed to do it in exchange for $20/hr. I told him she probably had a crush on him and he could have gotten more out of her but he was a good guy and didn't want to mess with that.

My wife’s is $10 a month

She is free for tributes. $500 if I bring her to you, you have to wear a condom too...

normality
 

Remember. For some Couples everything has to seem "acceptable" according to strict family standards. So no matter what happens, who she performs with, her Wedded Relationship has to appear "normal and ongoing". So "hoops have to be jumped through" to facilitate this. Like wearing/discarding Wedding Ring according to circumstances. Excuses have to be contrived to promote circumstances to either see, or avoid being seen, with her real/actual Sexual Partner. That way, the extra marital relationship could last an actual lifetime !

Nope, she just changed it to a free account. Turns out my wife is a sl*tty girl for free lol

As it turned out, it cost me a lot. She took half of everything, plus all the pussy. Still love her and I kept all the pics as trophies to enjoy and share here. I get payback every time some stranger jerks to her.

A friend made an offer
 

We were camped out with a friend who has been pretty successful financially. He said, "I really get off on your wife. Do you think she would spend the night with me for the right price/" I replied that I really didn't know. He said, "I am prepared to pay her $1,000 for the entire evening." I told him I would ask her. When I gave her his proposition, she said, "Just how kinky is he?" I told her I had no idea. She said, "Tell him that he can't do anything real kinky that I object to." He agreed. Then she said, "Will I get to spend the $1,000 any way I desire?" I told her that she would earn it and could spend it how she wanted. She agreed to do it.

Afterward, she told me that it was really great sex, and that she had always wanted to do him. The fact that she got the $1,000 was icing on the cake as she put it. I asked her if she would do it again. She said,, if he ever asked, her price has gone up to $5,000, because he told her that she gave him the best sex he had had in ages. He lives on the other side of the U.S., so her getting extra spending money frequently won't happen very often.