no such reference/formulation..example..a logo design..how to charge a client?..some says..based it on the hours u spend?...then how much is an hour's worth of your time?..u might spend an hour on a simple logo..but u think it looks damn cool..doesnt mean u gonna charge them peanuts..right?...so charging by hourly
only works for certain cases..maybe u can start from your own judgement..base on the size of the company (local..international)..your involvement in their future business..maybe tie the logo cost with other freebies like letterheads/invoicing/namecards..give a package deal...then lump up the sum if you decide to charge a bigger amount..advertising/design is a free market with free and wide endless invisible boundaries..muchless nowadays its not about how good your design is..more or less..its about who u know in the companies...and who wants a piece of the action...*wink wink...best is to try to get some inside info from the client previous charges by other design company...then see if its a reasonable billing...if u got no way to do that then i guess i gotto apologize that i answered your question with another question.