The backpacker district of Pham Ngo Lao in Saigon is filled with women trying to coax men into their massage parlors, not dissimilar to Thailand. My experience in Thailand, however, was that the women were still well-trained in massages and if the topic of sexual favors in exchange for money was never brought up, you walked out with some knots rolled out at a bargain price.
Seeing the obvious sex tourism here in Pham Ngo Lao, I asked a local to take me away from the backpacker district for a proper "no sexy"massage. Walking in, I paid $15 (higher than Thailand), and naively proceeded upstairs. The masseuse proceeded to lightly massage me when she grabbed my attention and demanded money to massage "my baby." I said no, to which she began to become anxious and upset that she wouldn't have a short session with a cash bonus to walk away from. After expressing my disappointment and refusal to tip for a service I was declining, she began to beg and say she was hungry and received no salary from the parlor. Whether the latter fact is true is questionable, but if it is, it shows the obvious demand for sex the tourism industry brings here.
The women have transactions which earns them $10-$20 quickly without a demand for a salary because stepping in is the entrance fee paid by a patron, so the parlor is satisfied. This way she can get high turnover. Unfortunately, I made her work for it and it was obvious how untrained she was in giving any semblance of a real massage.
My hubris led me again to a different massage parlor where I explicitly stated I wanted a foot massage. Same story. Only after turning her down did she actually try to give a real massage, although she tried numerous times to coax me again.
Can sex have economics? Clearly so. There must be a study out there that analyzes this stuff, but it's obvious how many tourists come here to have a meal, drink some cheap beer and get jerked off.