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It occurred to me that this guy has an awful lot of control over her life. Should she decide for any reason to withdraw from this relationship, who will pay for her expensive apartment? It goes beyond losing expensive baubles. She can't simply "stop" without literally months of planning in terms of finding another way to pay for her lifestyle (not to mention food and shelter).
And who's to say this guy's decision to offer her a "deal" rather than just ask her out doesn't out him as a cold-hearted control freak who is incapable of emotional connection (at least with her) and sees her as some sort of possession?
Maybe we want to see him as Richard Gere's Pretty Woman character, with some emotional wound that she is somehow salving with her body. My guess is he's just sort of an unemotional asshole who doesn't care that much about her and/or feels he can only hold onto her with money. Hard to tell.
In reality this little arrangement is one where she has little power if he decides to discard her or if he refuses to "let her go" amicably. Either way she could find herself suddenly without resources, or worse.