I sell packages which includes initial research, a certain number of comps, and a certain amount of edits. I usually offer clients three tiers, starting at $350 for a minimum three comps, 2 edit rounds, 3-7 day turn-around; $490 for up to five comps and five edit rounds, and $630 for up to seven comps and seven (essentially unlimited) edit rounds. All packages include deliverables (source files, pre-sized .jpgs, B/W versions and whatever else is appropriate). 50% kill fee if I don't come up with anything they like. All rights.
Naturally, everyone goes for the $350 package, and 90% of the time I get the job done, everyone is happy, and I make money.
This is for small, locally owned businesses that usually come to me for sign work. I don't get big corporate jobs, and honestly, I am not set up to do the kind of initial research, market testing, and branding development that would be required for that kind of work. A full service design studio with multiple employees with specific expertise is better equipped to handle those demands.
Illustration work is handled differently, usually with limited rights.
The sign work is priced separately. Most signs I do only require minimal design work (basically a layout for production), and that is built into the price (sometimes billed as a line item on more complicated projects).