If you want to get your money's worth, hunt down a Njerp and let your Companion take the lead. Either he'll win and you get the spoils, or he'll lose and you'll have to clean up and STILL you get the spoils, including whatever the Companion possessed. The loot will usually be worth much more than the cost of hiring and paying off the Companion.
For work around the settlement, I've found them very useful. When they fell trees, I haul them where needed. When I have enough, I have him make logs from trunks and make boards when I need them. They do a good job skinning and butchering, helping me move heavy loads, and any tasks I set for myself, like tanning, making logs, etc. While he works, I can perform other tasks, go fishing, craft, etc.
As for their worth, the FOOD is just the initial cost. I guess it varies depending on the length of hire. Thus far, I've only hired Companions for the longest periods so, when it nears ending, they expect some nice payment of gear or furs.
I've never had cause to regret their hire.