Something is cost-effective when what you get out of it is clearly worth what you put in — good result, low cost. The key point, and the one students miss, is that it does NOT mean cheap. A cost-effective machine might be expensive to buy; it earns the name because it lasts twenty years and saves money the whole time. So the word is about the ratio between cost and result, not about the size of the price tag. It belongs to business, government, and health writing: reports, proposals, meetings, budget arguments. In a report you will see 'a cost-effective solution', 'a more cost-effective way of doing this', and often the comparison that matters — 'cost-effective compared with building a new one'. Note the hyphen: it is standard before a noun ('a cost-effective plan') and usual after the verb too ('the plan is cost-effective'). Some writers also use 'cost-efficient', which means much the same thing, though 'cost-effective' is far more common.