Your sentence
Lo+compré+por+diez+euros.
Words in this sentence
él
he, him, masculine personal third person subject and disjunctive pronoun (used as a subject and after prepositions); it, masculine non-personal third-person subject and disjunctive pronoun (usually used after prepositions to refer to masculine nouns)
Pronoun
por
by; for (indicates something given in an exchange); through, out, via (indicating movement); across (indicating movement); about; due to, because of, for, for the sake of, out of (to express cause or motive); over; times, by, multiplied by; according to, for, regarding (to express opinion or something concerning someone); via, through, by (indicating the means of something); …
Preposition