http://www.ebay.com/itm/1979-Gibson-Thunderbird-Bass-IV-Bicentennial-Sunburst-Finish-Player-/281137995268?pt=Guitar&hash=item4175215e04 I just saw this and thought the neck heel looks waaay darker than it should, like maybe there was a repair and then black over spray. I know there was a repair around the nut area. I am comparing this to my sunburst '76 T-bird, and mine has a transparent back finish. Maybe they shot them like that. Anyone have a '79 like this? Here is a shot of my '76 neck heel.
I searched around on-line and it appears there were a few different finishes during the bicentennial re-issue (75-79) years. Some are dark mahogany w/no black burst (like the '60's originals), some all 'natural' (lighter mahogany), and some dark mahogany w/black-burst on the front only (like that one), and some with black-burst on front, sides and back. Seems to be many versions that were factory finished. You may want to post this on the Thunderbird Club thread for more insight.
The heel looks fine, Gibson did paint these several ways - I'd agree about the neck and at least want to see it in person. I haven't seen what these are selling for lately but that does seem a bit high. A properly repaired neck isn't bad, it just shouldn't have as high a selling price, FWIW I think this one's a little beat up for that kind of $$$