I wouldn't include a knife in a PSK in the first place. My opinion is that you should carry it seperately. If you lose your PSK, you still got your knife and if you want to do something with your knife, you don't have to make a mess of the tin. And you can use the space that the knive takes up much better.

If the knive in your tin is your back-up: I would remove it and replace it with a scalpel blade. The chanses that you lose your knife are slim, and if you do lose it, the scalpel blade is a acceptable back-up.

About knifes being very expensive: I use some good knives, the most expensive one was 20 Euro!
(my multi-tool costed much more, of course.)

'' The best knives are not always the most expensive ones.''

Make your own desicison and take care.

Jim