Typical "rule of thumb" is, when reselling software, half price is the best starting point...and works down from there...
Buyers are NOW exceptionally finicky, and even at half to 2/3's off, will not buy, as a sale will usually get them close,
and without the "transfer" hassles...
Pro Tools will usually sell used (current perpetual) for about $200 to $250...same as Cubase.
You can "ask what you want" but the likely of getting it is slim to nil....