Answer:
Puffery
Explanation:
Puffery refers to making hefty claims regarding product attributes and traits which represent a subjective and not objective view. Such claims are not backed by valid reasoning or valid evidences and facts.
In the given case, the art dealer claims his products being of high quality and appreciating over the period of next ten years. Such claims cannot be substantiated by any concrete evidence. As value cannot be ascertained in advance.
