I got it in a Humble bundle years ago for a relatively low price before the expansions and got those for free when they came out. I can’t speak much for the value of the current $40 price tag, but I certainly got my money’s worth.

The original game now called “Shovel Knight: Shovel of Hope” is well worth the $15 on steam for the standalone first installment though, if you aren’t looking to spend too much. Most folks do recommend getting Treasure Trove but I found I really didn’t play the expansions much myself anyway.