This image is a personal project, so doesn't belong to anyone else, i.e. a client. The full license for this image is £60 ($100).
Straight forward digital painting, all done in photoshop. I think this one took about a day or so. It is a concept for a large defense ship which protects earth from....em...aliens - yes that's it!
An image similar would take a day or 2 (including revisions). The cost would be around £200 ($320).