We were there around our anniversary and my husband had one each of my DS and DD done outside the Brown Derby. Wonderful!!! Framed and all I think it cost around $15 (several years ago). Still, for a purchase at that cost that is that special is a steal at Disney!
My advice is to watch the artist do a couple and see what you think before committing. This artist at BD did the kids' while we were waiting for our PS time (about 15 minutes).
Also, another fav of mine are the silhouettes (sp?). We had our kids (together) done at France in Epcot. It was cheaper to get 2 as they can cut them together (maybe?). So we got one for us and one from my mom. This was done about 7 years ago. I plan to get another in Feb and hang with our old one. DS (14) should love that! Ha!