because they can.
not to get overly reductive, but that's the whole supply and demand thing. when supply is restricted, you can't increase profits by selling more, so prices go up. no one is undercutting you because they don't have any more supply than you do.
and, you know, companies can get it wrong too. like if you pay any attention to business news, you probably heard this week that target mumped up their demand projections hugely and is going to lose a crap ton of money as a consequence.