Explanation:
let's bring everything to prices per full pound, and then we can compare the prices directly.
ham $3.50 for 1/2 pound
2×3.5 = $7 for 2×1/2 = 1 pound
turkey $2.25 for 1/4 pound
4×2.25 = $10 for 4×1/4 = 1 pound
salami $1.75 for 1/5 pound
5×1.75 = $8.75 for 5×1/5 = 1 pound
American cheese $1.70 for 1/8 pound
8×1.7 = $13.60 for 8×1/8 = 1 pound
Swiss cheese $1.25 for 1/10 pound
10×1.25 = $12.50 for 10×1/10 = 1 pound
so, we see the cheapest meat is ham, and the cheapest cheese is Swiss cheese.