I can't imagine a situation in my own household where this would occur. She's much more likely go have an affair with a civvie.

The situation you're speaking of might pertain to a household where appearances in the marriage had to be maintained. So, paid relationships for both spouses are better.  
In that case, I don't see why the man would have a problem with it

Or at least a discount every now and then.

The only reason I got into this hobby was the miserable sex life I had at home.  It was once a year for a few years and for the last four it's been non-existent.  I tried various remedies (talk, joint therapy, individual therapy, blah, blah, blah) but nothing worked.  We do/did other things reasonably well together, like raise two children and travel, and we're compatible culturally and politically.  At this point in my life my sexual frequency needs are modest, so an FWB and an occasional escort visit takes care of it.  

But if she has or rediscovered a libido she is hiding, I would not be happy.  We could work something out and stay together, maybe, so we could each have our itches scratched sometimes by younger, better looking sex partners.  But I would be pissed to find out she was doing it on the side and still ignoring me in bed.

but wouldn't know for certain until it happened. Sex is just sex to me at some point and the emotional attachment is different. It'd be much easier to deal then her cheating with a friend or co worker... I personally love the experience of sex with someone new the first few times, it can be amazingly hot and after years together it becomes stale. Anything to liven it up is a great thing.
       

You are making a huge assumption there, blondiegirl.  If a married guy is here hobbying, you assume that the wife at home would be able to charge money for her body/sex skills. I, on the other hand. would assume the guy is here hobbying because there is no sex happening at home.  
Why do you think guys look for a girl friend experience and not a wife experience ??  What man wants to pay for a woman that hasn't been near a gym/yoga/pilates in her life,  that lays there like a corpse,  hasn't worn sexy clothes/lingerie this century and thinks watching Honey Boo Boo is the highest form of entertainment??

So to be sure I understand the scenario,

you mean my wife pays a male escort to go in the bathroom and jack off?

although I was completely unhappy with my sex life when I was married

I never cheated, in fact I can say I've never cheated on any woman I've had a commited relationship with (close, but I resisted). But I also didn't stay in relationships I wasn't happy in for a substantial period of time. So, and this is my integrity, I don't agree with either the man or the woman cheating on the other. I do not impose my integrity on other people though, and I'm not a man of faith so my integrity is not based upon some unseen entity. I just feel a promise is a promise until you both feel that going your separate ways is best for each other. Now that I've found the hobby though, I don't ever foresee myself pursuing a civie relationship again. There just simply doesn't seen to be an upside. That's my opinion, I didn't charge you for it, and that's what it's worth.

so the specter of "double standard" is difficult too apply.

It would be such a beautiful thing! Our whole relationship might change for the better. You see I am a little progressive in my thinking and would be happy to know she shares my feelings

My wife has seen male providers....

She has seen both male and female providMmt.ers and "johns" of both sexes. We have an open relationship that allows both to pay for it or be paid. There are rules of course but as long as she abides by them I am fine with her seeing male escorts, female escorts, or paying clients. In fact last Christmas I gave her a MFM romp with me and a male escort I flew in as the local male escorts failed to excite her.