5* - 700 + 300 + 100 = 1100 CE

1* items cannot be upgraded to 2* or above, so they don't count.

2* items can be crafted entirely on mist, so they don't count either.

For the rest of the upgrading path, you can use your 100 mist as a discount.

You can already get rid of useless gear by selling it to a vendor. You won't get that much compared to the cost of the item, but the option is there if you really don't want to keep the item.

Would we be able to disintegrate equipment obtained through boss tokens? If so, this could make Firestorm Citadel and the Royal Jelly Palace even more popular than they already are, since you'd be able to get even more energy from the token equipment for those two stratums (strati?).

Royal Jelly Palace:

• Currently, you can get a Brute Jelly armor piece for 15 Jelly Gems. You can then vendor this piece of armor for 3500 crowns. Assuming you get 3 Jelly Gems from each run, this is 700 extra crowns per run.
• With the disintegration feature, you would be able to disintegrate said Brute Jelly armor piece for 75 CE, or about 5250 crowns (assuming an energy price of 7000 CR per 100 CE). With 3 Jelly Gems per run, this is about 1050 extra crowns per run.

Firestorm Citadel:

• Currently, you can get an Ancient armor piece for 30 Almirian Seals. You can then vendor this piece of armor for 30000 crowns. Assuming you get 3 Almirian Seals from each run, this is 3000 extra crowns per run.
• With the disintegration feature, you would be able to disintegrate said Ancient armor piece for 825 CE, or about 57750 crowns (assuming an energy price of 7000 CR per 100 CE). With 3 Almirian Seals per run, this is about 5775 extra crowns per run.

The differences aren't quite as large as I thought they'd be, but that's still more value to two stratums that people already run more than everything else.

@Oceanprince A hacker could already get into someone's account, sell all of their equipment and materials to vendors, and make off with the crowns gained that way. The only difference between that and your scenario is that the hacker would get more CE and crowns from the equipment by disintegrating it. Then again, the increased gain from the disintegration feature could cause said hacker to be more motivated to hack accounts.

Lets try this in reality, I make something. It takes energy to make this thing. Do I get energy back when I get rid of it? No.
Energy is something that is used to power stuff and ends up as heat.

Just sell to the vendor, they give around 450 ce for 5-star items (30k cr). They take bound equipment, too.
Trinkets only get you 10k cr for a 5-star one, though.