I can only tell you from years of experience, it very much depends on the chemistry between you and the girl, which may change and get better or worse over time.
I have found many pse girl who are thrilled to have a $500 meeting and give a much more spirited session than many other girls demanding $1k. In fact, imusualy find the $1k girls have more of a "diva attitude about them, and the clock seems a lot more important to them.
If you feel like spending $1k, my advice is to get a good $500 girl, enjoy yourself, and tip her an extra $500. She won't hesitate to take a second appointment with you. And you will enjoy her a lot more.