This is nothing new. Before the steam deck came out, Handheld PCs have already been ~~overpriced~~ expensive. Other manufacturers haven't bothered about affordability before, during ot after the steam deck.
That said, Gabe Newell said the steam deck was priced "painfully", which means they probably had very low margins on the hardware and are making it back on sales on their store. Other manufacturers do not have that luxury.