A few posts on another thread (not primarily about this) have got me thinking.
In my local ASDA Weight Watchers ready meals are £2 each. If I buy one for each night of the week (to make life easier for when I get home from work), that's £10 for a hot meal on every evening of the week. For this I get a balanced meal that, over the whole week, contains chicken, beef, prawns, pasta, rice and potatoes, vegetables and a variety of sauces. On top of that it's exactly as much as I need to eat, there are no leftovers, I am not using energy by cooling unnecessary stuff in the fridge. I don't need to keep a host of jars of sauces, oils and spices which would otherwise be needed to cook all this from scratch either. And finally, I am not using energy to cook all that from scratch, and then to wash up all that was used in the process. (I do use energy to microwave the meals, 5 mins each; and the microwave is very cheap to run.)
I can cook from scratch all that is in those meals. I don't enjoy cooking but I can do it if necessary. But I don't think that I would get that variety of hot food for just £10 a week. Furthermore, if I bought all the ingredients, they would be in portions much bigger than what I need for one supper. Then I would either need to freeze them; but also: does everyone who cooks from scratch only eat a WW meal-portion of everything before they freeze the rest? I find I eat larger portions if I cook. And while I'm not overweight, I really don't need to put on weight.
So I think eating ready meals is actually cheaper than cooking from scratch. It is also less time consuming (=more time for other things) and provided you choose the right ones and read the labels, not necessarily less healthy either.