I think you might have confused "underpriced" with "undervalued", but the concepts overlap. For me, there's not enough value in that Sanctum Art product, so it's overpriced. The value, I think, is what I can set; it's a judgement I make. Price is set by the seller, and if a lower price means more sales, and more total income, you can't call it underpriced. But we can still be undervaluing what you're selling.