Wow, people never get tired of this topic, eh? Without getting into the argument about whether or not you are getting more services or better services with someone who charges more, some of the other reasons may be:
Girls who work at massage parlours or agencies don't always get to set their own rates, they often don't have much say over what they charge, &, not wanting to start a fight, but when it comes to the micros/AMPs, unfortunately there are a percentage of them who are not in this industry by choice or are in it out of desperation, or are just working to pay someone back for bringing them to Canada. Another reason why many women who are not from Canada can charge less is because they are just doing this for a short period of time (maybe a few months) & then going back to their home country, where the money would be of much more value, so they feel like they are still making a lot of money in comparison. This happens in many other industries, for example, many farms or nurseries find it is cheaper to hire someone from, say, Mexico, & provide them with transportation, meals & accomodations, because they are happy to work for minimum wage, while a Canadian wouldn't because they would barely be able to live of of that. Then they return home, where the cost of living is much less, & the money goes much farther, so they feel that they have earned a fair wage.
PS - there are a lot of Caucasian SPs who charge less than $300 an hour, & there are also a lot of Asian or other non-Caucasian SPs who charge more than $60 for 45min. It is not so black & white to assume that it is solely a race thing & say things like "why do white chicks charge so much?" A big factor in it is probably whether someone is a Canadian Citizen or not, since many Asian or non-white SPs who are Candian citizens, speak English fluently, & have lived here their whole lives (or most of) charge similar rates to what comparable white SPs charge. It also depends on whether somone is independent of works at a micro or MP, since in general an independent, regardless of race, is going to charge more than someone who works at a micro or MP. And, yet another factor, is exactly what services are included for the price. Many MPs may charge only, say $100/hr, but each additional service on top of the massage, such as BJ, kissing (if even offered), Digits, COB, & so on, let alone FS, cost you more money & often you have to stop what you're doing & tip her before continuing, whereas the girls who are charging $200-$300/hr include everything in that price (other than of course Greek & in some cases BBBJ).