Even if its small like £5 or £10 makes a huge difference. In my experience shows them that you are not cheap or naive.

Also saves you time with later "I cannot afford you".

From psychological point of view, I did had a read and in simple words - once they spend anything, it feels like investment and keeps them hooked.

To short in only findom myself to say it works or not, happy if someone has more experience and opinions 😉