An idiom meaning to take advantage of someone's weakness or situation (e.g., to charge a high price), or to size someone up; an idiomatic expression.
交渉相手が急いでいるのを見て、向こうは足元を見てきた。
Seeing that the negotiator was in a hurry, they tried to take advantage of the situation.
観光地の店は観光客の足元を見ることがあるので、事前に相場を調べておいた方がいい。
Shops in tourist areas sometimes take advantage of tourists, so it's better to check prices in advance.
上司は面接で応募者の足元を見て、志望動機の弱さをつついた。
The manager probed the applicant's weak motivation in the interview, sizing them up.