I don't keep a specific BOB or 72 hour bag, per se'. What I do have, however, is smaller "groups" of items, that can be combined to create one quickly, should the need arise. Basically, I have a prepared camping backpack with some basic equipment, that can be supplemented at any given moment, with items that are stashed in a vehicle the house in a matter of minutes. The pack goes with me pretty much everywhere, because it's not cumbersome, and can be quickly adjusted to whatever the situation (for example: I can quickly grab the first aid kit and emergency bag from any of the vehicles and throw them in before abandoning it on the side of the road. Let's call it a "modular" system and mindset. But this is more of a discussion for a BOB type thread....
But as it pertains to knives:
Every emergency kit has a 2.5" - 3" folder in it of some sort. All are old EDC blades that have been replaced over the years, so there really is no 'new' investment in them, as they're knives I already had that weren't getting used. Prime example would be the Kershaw Blackout in the bag in my truck (I actually prefer it to the Blur). Durable, affordable, and something I'm not gonna worry about losing. But really, I EDC Manix 2 anyway, so I don't worry about what folder goes in any bag, even though there's one in each.
In the backpack itself, I keep a few knives.
- Again, there's an old folder, just because (not sure what's in there at the moment, but it's there). This is strictly a backup to my EDC, or if I need to hand it off to someone.
- Gerber BG Ultimate (laugh all you want) which is a decent size, and serves all my large fixed blade needs. The integrated sharpener and fire-steel are a nice addition (even though I have dedicated tools for this) and the price is right, at around $50. To do it over, I'd probably go with a Prodigy, LMF II, or similar, but so far, it's served me well around camp and in the woods.
- There is usually one of two, small 2.5" - 3" fixed blades as well. These usually float between the bag, the center console of the truck, or on my belt. One is an old Western W82 (hunting knife) and the other is an old CRKT Stiff KISS. Both were free to me, but could probably be found used at a flea market or gun show for $25 or so. If I was gonna go buy something for the pack, on my budget, I'd be looking for an ESEE 3 or similar.
- LM Wave multi-tool, which again, floats in and out of the bag to either my truck or belt, depending on day and situation. It's my primary multi-tool, so it's never far from me.
Like I said, my pack serves multiple functions, so it's almost always within arms reach anyway. Being winter, it's in the backseat of my truck right now, serving as a cold weather get home bag. When I travel, contents will get shifted around a bit to reflect what I might run into then. And during camping season, contents will get shifted around yet again for hiking and such. But those are the knives that usually live in it, even if they get shuffled in and out from time to time. Bonus is, since it's almost more of an EDC bag, all the tools in it get used on a regular basis, which means I'm very familiar and comfortable with all of them.
Don't know what his budget is, but for my knives (and my whole modular BOB/get-home system), I've spent very little, instead opting for things I already had on hand that either weren't being used anyway, or are integrated into my daily routine. My set up is more about mindset than a specific gear package.