Question about upgrade waitlist for international flight

https://preview.redd.it/2v94m9c0lktg1.png?width=2434&format=png&auto=webp&s=f65a2293279b83c6dfd07f3a8d590956883a28c8

Hello everyone, this is my first time doing this and I wanted to confirm my understanding.

I have a flight in 3 weeks and I wanted to try upgrading with points. I do not have any United status and purchased an economy seat. From my understanding, if I pay this miles rate, I am only joining the upgrade waitlist (which is affected by status, purchase ticket, availability etc)

I understand the chances of upgrade are slim due to me not having status. So if I were not selected, I would get the 30k miles and 550$ refunded. But if I was selected, would this be the only cost? It just seems too good to be true so I wanted to clarify.

Thanks in advance!