Economics 101: Supply and Demand.
If the supply is limited and demand is great, up go prices, and some customers will miss out because they are unable or unwilling to pay the prices.
If supply is plentiful, as it is in the sex industry in Perth, prices will vary depending on the quality of the service but should be competitive, which in general they seem to be if we compare like for like.
WLs are business women. In a competitive market, a business only prospers if it provides goods and services that people want and for which they are prepared to pay. If a business provides a substandard service or overcharges, it will be found out and will disappear. That's how the market works.