Which preposition does one use to specify the price of something after verbs "ankaufen" and "verkaufen"?

Answer 1

I believe it is the same auf Englisch. I never really heard "ankaufen" being used over there only "kaufen." With being said perhaps "ankaufen" is more professional or formal.

Examples:

Ich verkaufe es für €10.

Ich hab das für €5 gekauft. Wie billig oder?

I am highly confident that ankaufen would also use the same structure using "für."

I hope this answers your question.