Don't fall in to prossie maths. There lies insanity.
With 2 girls, it is less work for them than one. So I expect big discounts off 2x the in-call rate. And for me it is 100% an in-call - they are not in my hotel. Not my problem if one has to move to a new place for the next punter.
Think about what you want, not about what you would do if you were an escort.
And all the numbers you quote (I hope they were just maths examples rather than what you are thinking) are crazy. It is just sex, not football. £100 per hour each is more than fair.
She did not try to rip you off. She noticed you would pay too much, so asked for even more. Not a rip off. Just assumed you were a mug. Are you? It seems you said no, so it seems you are not a total mug, but anyway no foul. Similar to a rip off, but not the same. If you paid £550 you might be a mug. Please post a review and we will let you know. If the sex was dual anal with filming and the best sex of your life then perhaps not.