How much should I spend on a quality 3-season sleeping bag?

Across the reviewers we read, $100–$150 buys a respectable 550-fill down or quality synthetic bag from a reputable brand, $200–$300 gets you 800+ fill power and ultralight construction, and bags under $50 are generally fine for warm-weather car camping but underdeliver on the 'all-season' claims printed on their packaging.