Most of the truths that you hear in a good therapy session will come out of your own mouth. You just didn't know they were in there until the therapist guided you to them.
Try to think of "trust" more in terms of safety. With a good therapist, you can trust that if you share your truth with them, with all it's ugly dark aspects, that they will not use that knowledge to harm you.
If someone is crying, you are getting emotional feedback from that person that they need help. They could cry for any number of reasons but the feedback they provide you by crying remains the same until you discuss it more. Paid feedback or not - outsiders will provide you similar feedback that will be relevant to you because they are able to empathize (that is if you are honest).
But I get you. if you think of paid feedback as fake reviews on playstore, you will get discouraged. It's hard to give a fake plausible review and it's quick to spot for human interaction though.
For you, it sounds like you think that the therapist "might just be doing it because I'm paying them", and that their emotions care towards you might not be genuine? Maybe that you want a kind of selfless care and the monetary aspect would make it feel less selfless or sincere?