echo what's been said here, and add - do lots of market research. Asking on TAS doesn't count, lots of the information - whilst good - may not be as relevant to your situation (and location) as the research you do yourself. go on bigbarn, find all your local farm shops, visit them (web or in person) an gather prices, go to the main towns near you and visit the butchers for prices. Gather the highest and lowest priced sausages in each shop, and each type of shop.
you are not aiming for people who say "I could buy twice as many in asda".... those people are welcome to asda.