Once we elected to change from SE to PE visas, we were briefly converted to the SE and then the PE visas. It was not possible to go straight from the lifetime version to PE, but the process was done seamlessly on our end. My wife and I retain the right to sell our visas one time, but the next person would only receive our remaining years. We have no plans to sell them.
Thailand Privilege has a flat rate they charge for eligible transfers, and that fee is non-negotiable. I don't remember what portion of the total we paid that was. Whoever is selling the visas sets their own rates in addition to the flat rate. The couple were eager to return to Russia, which affected our price. We purchased both visas for a total price of 1.5 million THB (which included the couple's fee and the Thailand Elite fee) That was an exceptional deal as far as I can tell, given that the Priority extension, 20-year visas were 1 million THB each at the time, which itself was a good deal too. At the time, the Elite Ultimate Privilege (EUP) visas, which is what we now have, were 2 million each. So that's a 2.5 million THB savings. One other detail is we were required to pay in cash which was a little odd but not a big deal since the transaction took place at Bangkok Bank.
I was ignorant about how all of this worked until I discovered the secondhand visas on the website BahtSold.com. At first, I thought my wife and I would be getting lifetime visas, too, and did not expect any further benefit. We were lucky to have a very knowledgeable Thailand Elite Staff member who explained all the options clearly. Once I understood everything, I realized this was the best deal I'd get, and we went for it. I had not planned on receiving the "benefits" and likely would not have paid extra for them, but my wife and I enjoy them immensely, so it all worked out in the end.