Shovel Knight has sold 1.2 million copies, 1 million sold digitally (Details inside)

[Skullwaker]

Teeqoz said:

So? Gravity Rush Remastered was also 30$

Yep, and still sold significantly less than Shovel Knight. Even with SK being digital exclusive for more than a year before its physical release.

Honestly, price is only so much of an advantage. It doesn't guarantee success in every instance.