I think its a valid idea. First, things I wouldn't put in it. Anything with an expiration date at all. You don't know when you're coming back to it, or how much you'll maintain it so it's kind of a waste of money to put anything that might expire on you in it. Second, like you say, nothing expensive. I would say probably nothing over $50 at all and nothing over $20 that hasn't been thoroughly used once.

What I would include is at least one change of clothes. Probably a change of pants, two shirts, two pairs of underwear, and three pairs of white athletic socks. Then a good but old jacket, something I'd replaced with something newer. An old pair of running shoes, or old pair of army boots. Since I run regularly, I have shoes that aren't good for running, but aren't coming apart at the seams either same goes for boots. Finally, work gloves, a ball cap and a winter hat (probably something ugly I don't wear, or a black army hat now that we've changed to grey fleece). An old towel, either something bleach stained, or a brown army one since I always have plenty. Maybe an old blanket or sleeping bag if I had one. I'd bag all the clothes in the big 2 1/2 gallon ziplock bags.

Then a few tools, Swiss army knife and/or a Mora knife, army canteen (empty) and canteen cup, pair of pliers, 550 cord and duct tape. Probably a full box of strike anywhere matches double bagged in ziplock freezer bags. A box of emergency candles. A first aid kit consisting of bandages and tape (again nothing perishable). Finally probably a notebook with the front part full of useful information and maps and the back blank. And several wooden pencils.

I wouldn't include any personal information in a kit of this format. I'd instead put copies of a few important documents in an envelop and leave that directly with someone or with an attorney.

That's not a complete list, but pretty close for me I think.

If the whole thing cost more than say $50 in new stuff I'd consider it a failure. Work gloves, matches, candles, first aid, maybe notebook and pencils, duct tape and 550 cord and ziplock bags could be new. Nothing else should be.