Never he had imagined that his painting would sell at such a high price without much of his pieces circulated in the market before. That wasn't how paintings work in the market. The painter still takes a lot of time to get recognized before his art gets noticed. Until and unless a person finds some emotional attachment with the painting... and his painting wasn't that complicated to determine.
Now personally witnessing the scene... He was confirmed that there was something fishy going on between these two. David buying a portrait of a random girl couldn't be incidental in exchange for a huge price at that. He knew the girl already and have some emotional attachment to buy that painting from him and here he thought he was being lucky.
Alex half smirks and Sabrina turns to him. "How do you know David?"