My question is: did Goldcar have any close competition for that rating?
Yes, there are a plethora of companies offering attractive prices but then pulling the rug from underneath you once you've been snared in, Goldcar have simply come out on top of all those other bad companies.
Avis are almost always the most expensive of the rental agencies so you should always take their figure as the highest, the equally reputable companies such as Hertz, Sixt, Budget, Enterprise will typically be cheaper than Avis but similar to one another. That price range is the one that you should be considering as realistic, without hidden fees or underhand selling and without the dubious practice of charging for damage not caused by yourself. Go any lower than that average and you're venturing into dodgy territory. Not every rental experience with those cheaper companies is going to be a bad one but the risk is high, high enough for me not to gamble on it.
Go to any major Spanish airport during peak holiday season and witness the queues at the Goldcar desk. They are huge which is testament to how they can operate the way they do, there are more people sucked into the cheap price than those put off by bad publicity. It's a gamble that Goldcar (and other companies) are prepared to take.