Do you buy that sloppy cheap stuff from the supermarket? I used to think "its just 45p, bung it in the basket" and slop it out willy nilly. Then one day the tub was just liquid, the next tub tasted horrid and I went back to making my own. Have done now for several years.
Shredded white cabbage
1 Grated carrot
1 very finely sliced onion (use a sharp knife but don't grate as it makes it too wet)
Basic mayonnaise (own brand, usually 45p for 500g)
Mix well in a large bowl.
Don't salt - there is usually enough in the mayonnaise. Some recipes add lemon juice and/or mustard - I don't, we are quite happy with the plain version.
Make it in quantities to suit the next few days as it will keep in the fridge.
I spend around £2.50 on stocking up the ingredients, this will make several large bowls when needed (about 8 supermarket tubs) until the mayonnaise is used up, and then when fed up with coleslaw finish up the cabbage and other veg as a basis for minestrone soup.
Have you seen the new TV programme about money saving? BBC mornings? I caught 10 mins of couple of mornings (light relief from the politics) and could not believe they still keep finding people with no idea of monetary control or thriftiness. Today, it was the idea, of "managed debt" - manage? £100K on credit cards? I gave up and went to thin the swedes and think about cheap cuts of beef and filling winter stews for a few pounds a pot.