In reply to brokenjockstrap:
£300 for 30 years use so £10 a year, not bad.
I have two bags, one cost £30 approx 40 years ago, the other retailed at £70 30 years ago though I got it trade for £40, filled with best eider down. Still as good as new, though not had much use the last 10 years or so. good for below freezing anyway and the old one is good for huts and summer camping.
Also, look at how much a good Goose down duvet costs, best part of £100 when you find them. Most have cheaper fillings.