First, consider your husband's position: Once upon a time, he met a really cute girl (you), who for whatever reason laughed at his jokes and made eyes at him and then unexpectedly did that thing in that place and it blew his freaking mind enough so he didn't hesitate to call you.
The Girl Friend Experience is just that: where a man pays a prostitute to act and behave the same way a new girlfriend does in the early-and-horny stage of infatuation.
After the financial arrangement has been satisfied, then for the duration of the appointment the professional showers the client with physical affection -- hugging, kissing, holding hands, praising him, asking him about himself, and acting utterly fascinated by everything that falls out of their client's mouths -- no matter how banal. All of those things are part-and-parcel of the infatuation stage of a relationship as it culminates with sex.
She is not just selling her body, here, she's selling her sexual interest in him. It shocks these poor wives to learn that their husbands were paying good money for stuff they didn't really mind doing at home -- and they can't understand why. The fact that a woman is willing to tend to his sexual needs in a way that flatters his masculinity and sense of self so much that many men experience an unadulterated surge of Alpha testosterone.
The core of the GFE is the sex act, of course -- but often this is limited to a long blowjob or even a lengthy handjob. So why does a man crave this bit of intimacy -- even with a stranger -- so badly he will sometimes risk everything to enjoy it? It's no secret why "sudden renewed interest in sex" is often listed as a sign your husband might be having an affair: a good GFE is like Popeye eating a can of spinach.
Here's the thing about bringing the GFE into your marriage. You must initiate it, and figure out when the best time to pounce is.