It depends on market forces and relative bargaining powers.
If you are Edison Chen at his prime, you don't have to buy her anything.
@sweetiepie will attest to that. She will suck your dick and allow you to take photos.
If you are the typical sinkie humbao beta male, then you must abide by
George Yeo's dictum - know your place. You will always be behind alpha male in the queue. As a beta male if you get to date a chiobu, her mere presence is ROI. If not, don't date a chiobu. It goes in this order:
1. unmarried chiobu
2. divorced chiobu
3. unmarried not chio
4. divorced not chio
5. divorced with a kid
6. bui bui, regardless of marital status