I'd say the bigger concern is spurious correlation. The two factors may very well be unrelated, or share a common cause (like drowning and ice cream prices -- t

I'd say the bigger concern is spurious correlation. The two factors may very well be unrelated, or share a common cause (like drowning and ice cream prices -- they're both driven primarily by heat). However, when talking about price and revenue it is legitimate to render them on the same chart, since revenue is a function of price. Steam in particular has proven to be a wonderful platform to demonstrate this phenomenon, as the elasticity of demand for games software is very high, and discounting even modestly generates far more revenue than you lose through the discount. Steam and the publishers benefit even more due to the low marginal cost of delivery, largely accountable to transmission costs and the marginal wear-and-tear on data servers.