I do the Mumsnet chicken AND the 12 meals from a pack of mince .. it took Mumsnet to show me that it's not normal to do so.
Just checked our Tesco favourites list for the size of the pack of mince. 500g or 750g are both on our favourites. I'd say I use a 750g pack for shepherd's pie + spag bol + chilli or lasagne, and a 500g pack for spag bol + chilli + lasagne.
The thing that you have to remember is that, for me, meat is a flavouring and a nutrition-booster. It's not - with the exception of the roast chicken part of the MN chicken - the 'main deal'
So for me, a shepherd's pie is as much about the carrot, the onions, the gravy, the leeks in the potato and the crispy cheese on the top as it is about the fairly small meat element. Spag bol is all about the tomatoes and onions and herbs and garlic, with the nutrition boosted by a little mince and the cheese. Chilli is about the above but also about the beans (I would say I have about an equal volume of beans and spag bol, plus chilli and cumin), and the accompaniments of guacamole, yoghurt, pepper, lettuce, tortillas / tacos or rice. Lasagne is as much about the extra peppers, tomatoes and vegetables in the sauce, the white sauce, the pasta, the cheese topping as it is about the small amount of mince.
It's like saying 'but you make a pack of frozen peas last for three weeks' - nobody would think that odd, but for us the peas and the meat have much more equal billing than in most people's diets IYSWIM?
Equally for the chicken (roast, cold + any variety of made up salads - lentil, curried pasta, bean, home-made coleslaw - pie, risotto or soup) there is no pretence that the risotto or soup are 'all about the chicken'. The chicken is subsidiary in the risotto to the rice, the cheese, the wine -or whatever has gone into the soup that day. It boosts the flavour (we buy very good chicken so that it really does taste of something), it boosts the nutrition a bit, the 4 dishes run together as a good menu for the week, but I am not pretending that we 'dine principally on chicken' for 4 days in a row.