Albert Barnes Commentary Numbers 22:15

"And Balak sent yet again princes, more, and more honorable than they." — Numbers 22:15 (ASV)

Balak, like the ancient pagan world generally, not only believed in the efficacy of the curses and incantations of the soothsayers, but regarded their services as strictly venal. Therefore, when his first offer was declined, he infers immediately that he had not bid high enough.