〜わりに（は）
Considering…, for… (result out of proportion)machine translation
FormationVerb/い-adjective plain form + わりに（は）; な-adjective + なわりに; noun + のわりに
〜わりに（は） says that reality does NOT match the level you'd expect from A: 値段のわりにおいしい (tasty for the price — i.e., cheap yet better than expected). Either direction works: better or worse than expected, as long as there's a gap from the norm.
Connection: noun + のわりに, な-adjective + なわりに, verbs and い-adjectives take the plain form. A is usually something with a scale to measure against — price, age, effort: 年のわりに元気 (spry for his age), よく食べるわりに太らない (eats a lot yet doesn't gain weight).
Compared with のに: のに expresses a clear contradiction with a sense of surprise or letdown; わりに is much milder — merely "a bit off, relative to that baseline." 安いのに美味しい sounds genuinely surprised; 安いわりに美味しい is just the remark "not bad, for the price." Since it's a relative comparison, わりに isn't used when A is a specific exact number.
Examples
このレストランは値段のわりに、料理がおいしいです。
Considering the price, the food at this restaurant is good.
祖父は年のわりに、とても元気です。
My grandfather is very spry for his age.
彼はよく食べるわりには、太りませんね。
He eats a lot, yet he never gains weight, does he?