Passage Summary: A music critic argues that you can't judge an underground band's success by their record sales because high sales might mean they've sold out, but low sales might just mean they aren't very good.

Conclusion: The sales figures of an underground rock group's recordings are not a valid indicator of that group's success.

Reasoning: High sales might indicate a lack of authenticity (being too trendy), while low sales might simply reflect a lack of musical skill.

Analysis: The critic is dealing with a 'damned if you do, damned if you don't' scenario where neither high nor low sales provide a clear signal of 'success.' To justify this conclusion, we need a principle that bridges the gap between the ambiguous causes of sales and the rejection of sales as a metric. Look for an answer that suggests a metric is invalid if its results can stem from factors unrelated to, or even contradictory to, the quality being measured. It is quite common in subcultures for 'success' to be defined by things other than commercial appeal, and the argument relies on that tension.