The nice thing about making them yourself like that is you can then buy the supplies in bulk and distribute through the various kits. It makes it worthwhile to buy that big box of bandages from sams club rather than 4 small boxes or the big bottle of asprin so the unit cost is very low. Then all your kits are consistant with the same contents so you always know what they have in them.
I need to redo my vehicle FAK's. I bought a couple plastic boxes with dividers but nothing fits in them well at all.