I'm in the process of finishing my basement right now, which is about 1300 sq ft. We had the house built a few years ago (kicking myself for not having them finish it at the time, but cost was an issue) and had them run the wire for the basement panel at that time. I spent several weeks doing the electrical myself and just had the drywall installed last week. I am by no means a professional, but I have been familiarizing myself with the codes and have a family member who is an electrical engineer (and who knows many electricians) to lean on for when I have questions and to make sure I'm doing things right. $20k - $30k seems OUTRAGEOUS to me. I probably spent in the ballpark of $1,500 for materials, which includes all the romex, AFCI breakers, junction boxes, sub-panel, some tools, and all of the recessed lights (I got the kind that clip to the drywall). I will say, that doesn't include the actual electrical fixtures (other than the recessed lights). If you have a lot of chandeliers, semi-flushed, fans, etc, those can start to add up. You should 100% get another bid. I'd be really curious to see an itemized list of the quote you did get.