How much are they willing to pay?
Because pricing all depends on complexity of the whole project. To me, that's the best way to gauge how much to charge.
If you have the resources, you can also 'sub-contract' through printer and provide the prints too so you can make a little extra cheese off the top and charge as a 'package'.
If you only doing the designs and providing the files for print, then you don't want to over charge because they are probably on a budget and still need to finance the printing part themselves.
Anyways, i'd probably just go off a set rate per hour (like $75) if you're assuming position as an independent artist.
I don't know of any set, standard rate to apply since there are a bunch of variables with these gigs.
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