Abbreviation of 'cost performance'; a colloquial term for the value or effectiveness obtained relative to the cost.
このスマホは安いのに性能が良いからコスパがいい。
This smartphone is cheap but performs well, so it has good cost performance.
旅行は高くてもコスパが悪ければ行きたくない。
Even if a trip is expensive, I don't want to go if it isn't good value for money.
このカフェは量が多くてコスパが良いと評判だ。
This café is reputed to offer good value because the portions are large.
Colloquial: the amount of satisfaction or benefit gained relative to the money spent; 'value for money'.
安い居酒屋でも味が良ければコスパは高い。
Even a cheap izakaya has high value for money if the food tastes good.
アウトレットで買えばコスパ重視で選べる。
If you buy at an outlet, you can choose based on cost-effectiveness.