Could be hit or miss, as posted above.
I am a federal LE unit supervisor and I have seen some of our cars go to auction in top condition for incredibly silly reasons, such as needing a taillight lens that took over a certain amount of time to arrive. "Deadlining" as we called it in the Army. We also have some people who love and hang onto their cars using their own funds for maintenance, until the day the wretched heap needs to finally limp to the auction yard. Two particular people in my office come to mind, one with a Dodge Intrepid and one a Crown Vic. I would not want to own any of those.
I have never attended a GSA auction, but have attended state auctions for 25 years, and honestly have probably made most of the money I have paid towards large expenses in life by buying auction cars and then fixing them up and reselling. You can walk out paying between roughly 5 and 10% of book value, however you may not know if you have a keeper on your hands, or a car in need of lots of work, or a literal piece of junk. Typical example would be the ex-state police Crown Vics. You might get lucky and buy a few that need nothing for a couple hundred apiece, turn around and sell them for a couple thousand and feel lucky, and then splurge on a cosmetically nice one and find out it is only good to strip and scrap. Really a gamble, but the more experienced you are at doing your own repairs, and in getting close with people who run the auctions or work in the fleet service divisions, then the higher your chance of success. Those of us who have plied the trade for so long have our secrets that we have culled over the years to make the experience much more successful.