Funny how this all began with a post about the season of Peace and Goodwill.
'Tis the season to be jolly, guys. 
The problem is, as the responses show/suggest this is not a hobby that gives off goodwill in anyway.
You are paying incredibly large amounts of money to spend time with people who if you weren't paying wouldn't even spit on you if you are on fire.
The only thing that makes them put up with you and give you a good time, is the fact you are paying them those very large sums of money.
If you start acting like you are friends and buying them gifts. You run the very large risk of the girl thinking even with the large sum of money, she wants out of this.
You buy her a gift and she thinks potential EAS here. If she thinks potential EAS then she will think to herself better get rid of him and block him booking me anymore. Or she will think I better give a more detached, standoffish level of service to nip this EAS in the bud now.
Or conversely, she will think. I have got this guy right where I want him. I can put a fraction of the effort in now and he is going to be happy.
Therefore that £5 bottle of wine and festive spirit towards her will mean that good regular you have is down the toilet and turns into a bad regular.
Its a sad fact of this business.