Yeah, my math was off a bit.

Seems that a good way to convert rat shillings to scrip is to buy Maniacs Prayers, up-converting to Sigils and doing excavations in the Hurlers. 12+ SPA for that, if properly equipped.

It has advantages over running through the bone market as there is no exhaustion cap, sourcing cost, or need to wait for a particular fad. The single action profit of adding a brass skull to a best fashionable skeleton is (.15*6500)+50=1025p (total cost of buying/adding skull is 6450, hence +50p), but for a bird it's 700p. Since the matter at hand is shillings to scrip, bird skeletons are not particularly efficient, especially since the CiS raised the base EPA opportunity cost for an endgame player to 5. Overall , that bird is a good way to go on bird week, but otherwise it's a relative loss. The value added per bone is at best a wash given that the EPA for the moonlit woods is below the opportunity cost (relative loss of 8E), so the profit comes entirely from the secondary reward, which is about 50E spread over around 23 actions.

Though that's a very rough calculation where I leave out a number of things assuming they'll balance out.

With an opportunity cost of 5E, birdwatching costs 80E for 72E of items. Not ideal.

Come to think of it, if assembling and selling a 7 headed bird takes 13 actions, and your profit is about 50E, you could have made 65E at the CiS instead. Clearly only sensible during bird week.

I'm sure I've made mistakes, corrections are left to the student.