Well even if they were interested in selling it, you would not make any money off it. If you look at the EULA for the Creation Kit, any mod created becomes the property of Bethseda - at least in the USA as I'm not clear on exactly how European courts would react to the EULA. Anyway, what the EULA says is:
If You distribute or otherwise make available New Materials [Mods], You automatically grant to Bethesda Softworks the irrevocable, perpetual, royalty free, sublicensable right and license under all applicable copyrights and intellectual property rights laws to use, reproduce, modify, adapt, perform, display, distribute and otherwise exploit and/or dispose of the New Materials (or any part of the New Materials) in any way Bethesda Softworks, or its respective designee(s), sees fit.
Which basically says Bethesda reserves the right to use the user-created content in any way it sees fit, including selling it and the creator would have no right to claim royalties.
The uploading of mods to Steam Workshop is essentially the same, the creator gives up all rights to Steam for the privilege of posting their mod.
However, you can post your mod to certain web sites and ask for a donation. This site being one - http://skyrim.nexusmods.com/
- that permits modders to upload a mod and say they are willing to take donations. The mod page has a small sign stating "Like what this author does? Consider donating money to this user through Pay Pal to help support and encourage them." so the modder is not being paid for the mod, but for the time and effort to create it.