Learn Spanish (Latin America): Yo compro carne cara, pero tú compras arroz barato. - I buy expensive meat, but you buy cheap rice.

Pero means "but" and it works exactly like it does in English. It connects two contrasting ideas. Notice how the sentence structure on both sides of pero is the same: person + action + thing (Yo compro..., tú compras...).

Do I have to include yo and tú? I thought Spanish usually drops them.

You can absolutely drop them, and compro carne cara, pero compras arroz barato is perfectly correct! However, including yo (I) and tú (you) here helps emphasize the contrast between what I am doing versus what you are doing.

Why does it say carne cara instead of cara carne?

In Spanish, describing words (adjectives) usually come after the thing they describe. So instead of "expensive meat", you say carne cara (meat expensive). The same rule applies to arroz barato (rice cheap).

Why does "expensive" end in -a (cara) but "cheap" ends in -o (barato)?