does it immediately degrade to Used when transplanted?
Isn't that the definition of Used? That it is second hand....? That it was configured and customized for someone else's body. And this is the reason why it cost less resources but more essence.
That's my take.
To further discourage my players from breaking down every corpse they make for parts, I also say:
1) all cyberware becomes Used immediately, regardless of previous normal/alpha/beta/delta status. What makes alpha/beta/delta special is how well they are engineered and customised for you, not anything inherent (and transferable) in the 'ware itself.
2) the listed price for cyberware is partly parts and partly labour. You're only getting fence value on the "parts" part. For invasive whole-body ware, like wired reflexes, the labour is a lot of the cost.
3) it's illegal stuff anyway, so even before the above you're only getting pennies on the dollar as it has to be rendered untraceable, stealth RFIDs eliminated, etc.
For example, they took out someone with ~1.25 M¥ of alpha/betaware, used a chop shop to dispose of the body, and walked off with maybe a few tens of k¥ in extra money for the cyber the chop shop took off her.