-->"How much does it REALLY cost to have a favorite?"
So, I assume you want YMMV contact with this girl, and want her to sit with you for a long time. If you're not going to get above-and-beyond service, if every guy who walks into the club gets the same service from her and there's no benefit to being her regular, and you're not interested in having her gift you a bunch of time, then there's no reason to want to be her regular. You can just hang out with her whenever you see her.
If you do want to be her regular, how much it costs depends on the club, the girl, what you want from her, and especially, what time you SC. If you pick the hottest girl, from the hottest club, and like to SC at midnight on Saturday, you're basically going to be JS69 junior.
For myself, I pick the hottest girl, and I SC with her during the slowest times of the dayshift. For me, I typically spend about 4 hours with her, and buy 2 VIPS ($200 total) and typically spend $60-$100 (let's call it $100) on booze and food... so $300 total per trip. I'll sometimes see her as little as once a month, and that still gets me solid regular status -- lots and lots of time with her in the club, texting in between, YMMV in the VIP. But there have been girls who drove me pretty crazy, where'd I'd go up to 5-6 times per month, which works out to .... fuck, ok, I don't want to know, no one tell me the answer.
So, how much does it cost to be a regular, where regular means "you get YMMV in the VIP and lots of time on the floor with her"? For me, for the hottest girl on dayshift, it's as little as $300/month, but you can multiply that number by 5 (do NOT tell me the answer. I flunked out of 3rd grade so I can't figure it out myself) to get the monthly max I"ve ever spent. You go for the hottest girl on the busiest hottest nightshift, I assume easily $1000/trip.