It depends on what kinds of staples Richard has available in his pantry. Initially it might be more expensive to stock up on grocery store items, but it wouldn't be long until all he'd need to get are the perishibles. If he asked you this question, then he must have access to the internet where he will find unlimited ideas on cooking for one.
If he is losing food through spoilage it would be better to purchase smaller amounts, wouldn't it?
A pound of hamburger (let's say 80/20) is still around $3.50. A package of buns around $1.50. He could get four big hamburgers out of that at a cost of about $1.25 each. A 5-pound bag of potatoes is around $4.00, but has several dozen spuds in it. If he cooked a couple medium potatoes in the oven or microwave to go with his burger, he have a hearty side dish for around .50 cents.
There are many, many ways to eat interesting meals at home much cheaper than eating out.
Richard...spend some time reading the left-over threads here...you'll get dozens and dozens of ideas on stretching your budget while eating well.