As you wander round the supermarket wondering what to eat, your eye might be caught by the ready meal packs of sausage and mash. I myself have been tempted by these in the past, but never found them good value.
I find the mash is like wallpaper paste and I begrudge spending over the odds on what can be made quickly at home, in the same amount of time, at a fraction of the cost. 
A typical bangers & mash ready meal will cost about £1 and consist of two sausages in gravy, with a dollop of mashed potato.
You really CAN make this at home yourself … and on a tighter budget.
Microwave Sausage & Mash
If, instead, you check out the cold meats aisle you’ll find packs of ready cooked cocktail sausages. A 400 gram pack will typically contain 40 cocktail sausages, with five cocktail sausages being equivalent to one regular sized sausage. At a cost of about £1.60 for 40 cocktail sausages, this works out at £0.40 for the equivalent portion to two regular sized sausages (10 cocktail sausages).
To microwave cocktail sausages just give them a prick (to stop them exploding as they warm up) and pop them into a mug, then microwave for 2-3 minutes, giving them a quick stir every 30 seconds or so.
To make the mash, you can either use a microwave steamer, to steam potatoes in a microwave, or, simply make up some instant mash. Instant mash has come on in leaps and bounds in recent years. My current packet tells me they are 99% potato. No room for fillers, it’s just potato! I make up the quantity I want, with a knob of butter. Typically, a portion of mashed potato will cost me £0.10.
You can use instant gravy, just a teaspoon or two is enough, to finish this dish off to match the ready meal that’s much pricier. Cost of the gravy is probably £0.01
So that’s bangers & mash, with gravy, at £0.51 instead of £1.
The instant mash keeps for months in the cupboard and cocktail sausages have a typical shelf life of 2-3 weeks, but they can just be thrown into the freezer; I portion them up in 5s, so I can just grab “1 sausage portion” at a time!