Well, creating a logo is a form of development.
But if you're selling to a domainer/reseller, they may not care for the logo.
If you're selling to an end user, again they may not care for the logo, especially if it's mediocre or doesn't capture what they have in mind for the site.
If I were you, I'd run an experiment and try this technique on half my domains and see if it gives better results.
Edit: I wouldn't spend any money on paying a designer to design the logos though. If you already have this skill and can pull something off, that's fine. But paying extra for someone to design them for you doesn't sound like a smart thing to do.