If you scratch the surface, prostitution is not a man buying and women selling - or vice versa - issue.
It is more like "I have money, you don't so I can buy your sexual favours" and "I have less money than I would like so I let you have sex with me."
I know, this view won't be very popular on a review board, because men AND women are in denial. Women like to think that they do it for reasons other than money, and men like to think they are getting it for reasons other than money
but if you look at reality, there are men who sell their sexual services to men and women all over the world. And sadly, there are people who sell their children for sex because they are desperate for money.
As long as men have more money than women, men buyers and woman sellers will be more common. In Africa men have no money, women tourists do, so this development shouldn't come as a surprise. People with money will always use people without money for sex. (see slavery for example)
Also, older women are in need of sex, because they are not desired by most men, so they go where their money can buy what they need.
I would say good for them!