how much would this cost?

a fiery dragon sword max damage (gold) with +28 foritude and plus 20% damage above/below 50% hp

+28 fortitude pommel = ~8k
Maximum +dmg option You can get with "while above 50%hp" is +15%.
Maximum below 50%hp is 20%.

Let's think about it as a req.8 15>50 one. Could be around 30-50k.
Req.8 20<50 would be like 10k.

k thanks

10k..not much

req8 15>50 60-75k