A "buyoff" (or buy-off) is usually a noun related to the phrasal verb "buy off", but the context here suggests the writer means "sell out"（卖完）.

Where did you find this sentence? It's written really poorly so I can't understand it. Buying off typically refers to bribery. For example, buying off a judge would mean paying a judge illegally to convince them to look the other way in a case.