Have any of you ever painted or refinished kitchen cabinets? If you painted them, how did they turn out and how expensive was it?

I have. I'm not sure if this is going to help though because it would depend on the surface material that you want to paint.

The one I worked on was an old kitchen but was still in reasonably good condition. The doors were made of what they call 'masonite' which is like a heavily compressed and very dense thick cardboard. It has already been sealed and painted at some time in the distant past.

Firstly, I washed down all surfaces with liquid sugar-soap to remove all dirt and grease. Then let it dry thoroughly before sanding it all with a fine grade sandpaper. This gives the new paint a slighly rough surface to grip on to. (Don't use a coarse grade sandpaper because it will leave 'cut' marks which will be hard to cover with the new paint).

I used an enamel paint, rather than a water based paint, because although it takes longer to dry it will provide a much harder and durable surface.

To apply the enamel paint, I used a small foam roller which gave a really smooth and even finish. And from memory (which isn't that great these days) I think I gave it 2 coats (maybe 3) with 2 days in between each coat. You will also need to give it a light rub with the fine grade sandpaper when the first coat has dried, to give the second coat something to grip...otherwise it will peel off.
Hope that helps. Happy renovating!

Oh, and it turned out quite good... nice and fresh. And cost about $50

Thank you!