Tin of tuna or 1x chicken breast, salad & 1 piece of fruit is maximum £2.50. I know which I'd prefer
Cost
Iceland sell 4 cans of tuna for £3; 75p each.
fruit - 50p.
tuna can + fruit = £1.25. (this offers the best value for money)
In terms of cost/nutrition, tuna sandwich wins hands down.
Chicken is more expensive.
And protein bar is even more expensive (though might taste great).
I keep mentioning cost, because for most people, cost is VERY important.
Protein Bars
For the record, I have eaten protein bars, when bulking, so I'm not totally against them. Protein shakes work out cheaper, though.
Protein bars usually taste nice and are an easy way to increase calories.
I can't imagine ever eating one when reducing weight, though - as these things are usually very dense in calories and will not fill your belly, so you will get hungry fairly quickly after having a protein bar.
Whey Protein Isolate
Getting back to the subject of supplements, I'm now having unflavoured whey isolate, and this stuff tastes nasty. I got this for a cheaper price than normal whey, but I cannot understand why anybody would pay extra for whey isolate vs concentrate. Unflavoured whey concentrate tends to be a lot more milky/natural in taste. Whey Isolate has a more acidic taste and its consistency is not as creamy.