I am pretty fascinated with the concept of "survival kits." I have at least four of the Ritter PSPs, and two or three of the newer SOL Scout kits. Lastly I have two of the UST FeatherLite 1.0 Survival Kits. That last one isn't very good but I'll confess I bought them because the zippered pouch is very nice! So I reused a couple items from the kit and mostly rolled my own using the pouch.

There must be a market for small kits since there are tons on the market. To me though the main use is as a starter/base to build a kit around. Particularly the Ritter PSP! It would be hard to find all the components individually for the cost of the PSP! That said I tend towards the same point of view as Hikermor. I've spent a lot of time in the woods, I'm pretty proficient and firecraft and can improvise shelter in a fair amount of ways. But when the chips are down and I'm in a genuinely tough spot I don't want a wire saw, a compressed towel and a $1 Chinese flashlight! I've never been in a truly dangerous survival situation although a couple times things could have went south on me catastrophically if not for a bit of luck. So my kits are a lot more robust than the old Altoids Tin kits you see "reviewed" on YouTube.

For $100 I could put together a kit that I'd feel pretty good about running with for my AO (western Montana and northern Idaho). The toughest part of hitting budget would be a pack to put it in but honestly I'd buy a $5 pillow case at Walmart before I'd let budget force me to leave the kit at home!

A rough draft of a $100 kit:

5-Star Gear Survival Woobie- $35
Cheap rain poncho - $1
AMK HeatSheets Blanket, 2 Person- $8
Cheap Space Blanket (but not the cheapest)- $2
BIC Lighter- $1.50
3 ESBIT- $3
3 Baddest Bee Fuse fire wicks- $3
Cold Steel Kudu knife- $8 [Note: If I could spare an extra $2 I'd go with a Mora]
20 Aquatabs- $1
1.5 L Nagene- $11
UST Signal Mirror- $8
75' Catahoula tarred bank line- $2.50
25 x UCO Stormproof Matches- $3.50
4'x6' Blue Tarp (Dollar General)- $1
1 x Tea Light Candle- $.50
Brunton Keyring Compass (nearly as large as baseplate version)- $6
Slim Rescue Howler Whistle- $5

Total: Exactly $100! To be fair this doesn't include a pack but I'd keep the Walmart plastic bag if necessary! These prices are realistic, and I have purchased all of the items for the stated price or less. Occasionally they were on sale and some items (like the whistles) must be purchased in a 2 pack to get that price. Obviously this doesn't include tax but most was purchased at Amazon with no taxes or at a B&M store here in MT where we don't have sales tax.

Will this fit in an Altoids tin? No! But could I spend an unplanned night out in the woods with it? Heck yeah! Depending on the weather I'd maybe even be cozy. The Survival Woobie is worth its weight in gold! You can use it as a blanket, zip it into a light sleeping bag or it into a tube that you can wear while you stand or walk. While it won't fit in a pocket it can be contained in a pretty small daypack, and it gives you enough capability to cover you immediate need for shelter, a means to actually store and sanitize water and to get a fire going pretty reliably.