Economics of Being Hugh Hefner's Girlfriend

From the perspective of a former girlfriend (and before that former law student):

Being a Hefner Girlfriend was a specialised job, not to be confused with being a Playboy Playmate. In fact, Girlfriends were not allowed to become Playmates because Hef had found that they tended to flee the Mansion as soon as they collected their $25,000 Playmate cheque. Girlfriends were given their own bedroom, an allowance of $1,000 a week in cash, a new car, free dental and medical treatment, almost limitless clothes, hairdos, make-up and facials and all the cosmetic surgery they could wish for – Izabella reckons Hef shelled out $70,000 a year on breast implants.

I would not have imagined it would be so, well professional. Like say, the oldest profession?

And then, of course, there was the sex – though surprisingly little of it according to Izabella. She reckons she had “less than 15 intimate minutes” with Hef in her two-and-a-half years at the Mansion – “I may as well have lived in a convent.” His main Girlfriend, Holly, shared his bedroom and presumably took care of his quotidian sexual needs – but Wednesdays and Fridays were Sex Nights when all the Girlfriends were expected to be on bedroom duty – though it was up to them whether they participated.

I mean this to empower, not to degrade: how is this not prostitution?