I'd love to hear some suggestions as well.
In my experience, I think it depends on the demand in your area (unless shipping) and the platform or venue where you're selling. I'm very new at this but my current pricing scheme for birds around the same age is around $10 for cockerels and $20-$30 for pullets. If it's a silkied then maybe $5 extra for that bird. Or $5 less if it's an extra long-backed or otherwise gawky looking bird. Selling on Craigslist seems to be difficult where I live. Selling at a swap, easier. If selling on Craigslist I may lower my price a bit to make a sale. Right now I've got a CL ad up for young cockerels at $5-10 and after two weeks I've only had one reply. I have an easier time selling large fowl.