there are manufacture thar make pre-made PSK (personal survival kits). Many of them are reviewed in the survivalkit section of this website

On the question of price, it really depends on what you put in such a kit. If you put simple and easily availible things, you can buy them in bulk and thus cheaper. If you need specialized equipment, which are hard to get and pricy. Than some pre-made kit are cheaper. Although i don't own the PSP survival kit. It does appear to have good price/quality ration.