What tipping looks like elsewhere
There is no single custom. Some independent readers, especially those who work out of a shop or at events, accept tips the way any service professional does, and a few dollars after a good reading is welcome but not expected. Some sites that bill by the minute add a tip screen at the end of the call, sometimes with suggested amounts, and a share of that goes to the site rather than the advisor. Some platforms do not allow tipping at all, so the advisor's pay is the reading and nothing else.
If you are on a site with a tip prompt, it is worth knowing that it is optional and that the advisor was already paid for the reading. A tip should be a thank you, not a second price. If you feel pressed to tip, that pressure is a sign about the site, not about you.
When a tip is a warning sign
A request for money after the reading is different from a tip prompt, and it is worth naming. If an advisor tells you there is more work to be done on your behalf, and that it costs extra, that is not a tip. It is the classic pattern behind most psychic scams. A tip is something you offer. A demand is something you should walk away from. The plain version is at is it a scam if a psychic asks for more money.
How it works here
Tipping is not expected, and there is no tip prompt. The price of your reading is the whole price. You saw it before you paid, and nothing is added at the end. Your advisor is paid for the reading, not for how long you stay on the line and not for what you add afterward.
If you want to thank an advisor who read well for you, the best way is to book them again. You can request an advisor by name, and the calendar shows their availability. Your advisor remembers you next time and picks up where you left off, which is worth more to a working advisor than a few dollars. Leaving an honest note about your reading helps too, because it is how the next guest finds them.
The plain answer
You do not need to tip a psychic. Where tipping is customary it is a small courtesy, not an obligation, and a good advisor will never make you feel otherwise. Where it is not customary, as here, the price you agreed to is the price. Spend the money on your next reading instead.