More than a bargaining chip, IMO. It's an irreparable loss to China.
They're strip-mining the daylights out of their own country for rare-earths, and DPRK is sitting on a lot of it. Loss of influence by China over DPRK will be an irreversible loss of that source of revenue, because China knows (or, it did) that they were the only avenue into the wider world for those resources.
And they'd get it for a pittance.
Not only that, but they also lose their stalking horse that they've used against us for decades in the foreign policy arena. How are they gonna eke more concessions out of us if they can't use the "we'll keep North Korea in line" BS?
Really, it's a 3-decker move. We get an ally that will now be an economic thorn in China's side (literally! if you look at the geography). China loses a boatload of future cash and it's one bargaining chip. And we help develop an economic renaissance in Asia outside of China, on terms frenly to the US.
Y'all Chicom observers catching all this?
If you need the executive summary, it reads something like this:
WE-ARE-FUCKED
Cao Ni Ma, Commies