Justify this

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It costs around $13 to buy a book at the local book shop.
It costs around $16 to buy the same book online at Amazon.

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It costs around $7 for a small garden salad at the shops.
It costs around $6 for a burger, chips, and drink at McDonald's.

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It costs about 30% more in usage to have your electricity come from renewable sources.

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The promotion of waste is played out as a game when a restaurant states "If you can eat this whole meal, it's free!".

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If someone can afford to pay for more of something, it is cheaper for them. But when someone can only afford a small amount it is more expensive. Like pay by the month v pay by the year insurance.

This
What if the cure for cancer was trapped in the mind of a child who's parents cannot afford to give them a decent education.