buying a masterwork version of an exotic weapon

[Fenix]

So I read somewhere that getting a masterwork version of an exotic weapon was significantly more expensive than the extra 300 gold it is normally. I can't find where I read that though and I am wondering if I imagined it or I read it from a non-legitimate source.

Does anyone know anything about that or did I imagine it?

[ElterAgo]

Only if it is a double weapon. Then you have to pay the 300 for each head.

[Darrell Impey UK]

That applies to all double weapons, obviously.

Quarterstaff 0gp, MASTERWORK quarterstaff 600gp.