What I find difficult to comprehend in this scenario - in any scenario of prostitution - is how much genuine pleasure the proposer/customer/John would actually get from buying somebody's (technical) consent.
Wouldn't it completely spoil things, knowing that the person you're having sex with would not remotely consider doing it without you paying them - they're effectively having sex with your money rather than with you?
I'd say it's all the same in principle, regardless of how much it says on your price ticket; but I reckon it must be even worse if you're a multi-millionaire (presumably a single millionaire wouldn't trade the whole lot for one short liaison) and you still can't find somebody who finds you attractive enough to want to marry/be in a relationship with you - for you.
Of course, I'm not for a moment saying that they should want to marry you only because you're very rich, but considering that plenty of ordinary non-wealthy people manage to fall in love and build happy, successful relationships based on what they each have to offer in terms of personality/character/intelligence/looks/status etc., you would think that having a yacht-load of cash on top of the other attributes you had going in your favour certainly wouldn't be a disadvantage in finding somebody.
All in all, being in a position where you feel the need to use your riches to buy people's sexual 'consent' does kind of suggest that your general personality in and of itself acts as a natural contraceptive!