PC on 2 perfet bows

How much?...

flatbow: 10-15k
shortbow: 5-10k

1) ~5k
2) 1-5k.

ow, i thought it was about 20k...... ok

The price of the flatbow depends on the skin: feathered > normal skin. But indeed I'm affraid you won't get much nowadays :S

i have a +28hp mod, does it work on that type of weapon? (i've never add a mod on any gold thing)
would it be more valuable then?

I wouldn't suggest replacing a perfect mod with a non perfect one, even though it is fortitude.

And adding mods to sell for more isn't a good idea most of the time.

Adding that mod wouldn't increase its value, PS - I didn't know that there was a Feathered Flat bow skin. But either way, I agree with the others and say that you won't be getting much for it.

Short answer: No.

Adding mods to items don't make 'm more valuable, they only help selling faster. And this mod isn't perfect, so I wouldn't have any effect on the price of the bow.