Not necessarily. A lot of our trash is in complex molecules. If the binding energy of those molecules is higher than the binding energy of the simpler elements/compounds that we get out then, in theory, the process would also be energy positive.
In theory it may not be that much. There's no reason you can't reuse the same few J to split several molecules, and capture it again for the next batch.
One probably can't get a resersible process, but just adding up the energy to break all the trash can be wrong by several orders of magnitude.
Yeah that was what I was about to say, fusion, solar, and other centralized energy tech (if we every readily deploy them) should allow us to trade more energy for more of the materials we need, and then as other commentators have said, the trash piles of the world start to look like just a bunch of raw materials.