Good points, sarah, but I don't think many developers do much to help themselves.

I have commissioned several developers to develop plugins with features that are based on, but go well beyond, free plugins that are available in the wordpress.org repository. Some of the customizations have cost $100s, and one over $2,000. All have been well worth the money.

In each case, though, the developer explained clearly (a) what the original, free plugin could do, (b) that they were available for hire to do related work, and (c) provided a link to where users could see what other work they had done. (They had also been very responsive in their plugin's forum.)

Most developers just don't do these things well. Plugin instructions are often poor, so users find that they have to fiddle with the plugin for a long time, and ask lots of questions, to make it work. This makes users feel short-changed, even though the financial cost to them was zero.

Second, most developers do a very poor job of explaining what custom jobs they do. Just saying that you're available to do WordPress stuff is too vague to be of any use. No-one is good at everything!

Third, most developers' sites are actually garbage. Even if they do bother to provide a link to their own space, it is usually so badly put together that I'd never commission any paid work from them.

Alternatively, even if the site isn't garbage, it's filled with totally unrelated stuff. Honestly, if you want to get me to pay for your services, I don't care about your views on God, or pictures of fluffy bunnies!

If you want me to trust you with my money (which I'm quite happy to do for the right work) you've got to show me that you really know what you're doing. The developers whose work I've paid for have done precisely that.