Whilst the £600 might sound a lot, it wouldn't take much for that to add up, even with fairly basic contents. I'm going away tomorrow, and in my small holdall, I'll have the following, with their cost to replace:
Bag: £60
Pair of jeans : £60
2-3 tops/jumpers : £100
2 bras : £70
knickers/socks : £20
Pair of shoes : £60
Nightwear : £30
Toiletries (shampoo, hair products etc) : £50
Make up : £25
Hair dryer : £100
Hairbrush : £10
Kindle: £150
That fairly basic overnight bag comes to £735.
Having said that, if my bag were lost for any reason, I wouldn't need/rush to replace most of these things. I have other jeans, and plenty of tops. I wouldn't miss the knickers and socks. Toiletries etc I'd obviously need, and I'd want to replace my kindle and hairdryer. So the immediate cost to me would be more like £300. But if my bag was lost in the circumstances you describe, I think I'd appreciate a contribution towards that replacement, but I don't think I could bring myself to look for the full value of what had been lost.
If nothing else, this thread has made me think I need to check the value I have on my house insurance for contents!