And most potential buyers would likely prioritize buying a PC before they consider getting a Steam Deck so it’s likely even more sensitive to price increases.
Also, the market eventually gets saturated when all the gamers willing to pay 400-650 dollars for a Steam Deck already have one. That's when a company usually launches the next generation of the hardware, or reduces the prices for the current generation to widen its appeal, or both. Of course, increasing the prices while not changing the hardware (and eliminating the most affordable version) is the complete opposite of this, so it will obviously lead to a sharp decrease in sales.