I'm not so good with the chemistry (no space, no availability, worried about where to store etc...), so I use tetenal colortech c41.
In Australia I get them for $44 au for 1 litre kit and $160 (or so) for the 5 litre kit. I prefer 5 litre kits, but our only supplier in Australia (yes, I can only find one!!) has run out. I normally get 25-30 rolls of film per litre before I give up (somewhere between $1 and $2 per roll depending on the availability of the larger kit).
Recently I tried Kodak Flex SM, it was cheap - $18 for the 3 part dev kit, but I dont like the colours
Looks like fuji may be next.