I have noticed on the forums that some people had said that you get more money if you stip your old ship of parts and then buy a new ship rather than just PX it
So here is my finding
Selling Adder (improved to mainly C class stuff)
Buying Cobra Mk III
PX
Cobra 379718
Adder -463057
Bal 83339
Ok so now I sold all the weapons on the Adder, and downgraded as many internal components as possible to E1's
Then bought the Cobra Mk III by trading the (slimed down) adder and paying cash and ended up 45,776 credits better off than the PX option - so enough to upgrade the weapons and cargo holds
So here is my finding
Selling Adder (improved to mainly C class stuff)
Buying Cobra Mk III
PX
Cobra 379718
Adder -463057
Bal 83339
Ok so now I sold all the weapons on the Adder, and downgraded as many internal components as possible to E1's
Then bought the Cobra Mk III by trading the (slimed down) adder and paying cash and ended up 45,776 credits better off than the PX option - so enough to upgrade the weapons and cargo holds