"If only I could go back in time I would spend all my money and buy 10 Tarmogoyf when it was first released, I would be rich now"
The short version of this is Etali, doing Etali things
Promos (P) Promotional cards - like the aforementioned Lightning Bolt from MagicFest - can come from events, prereleases, special products, store promos, conventions, Secret Lair drops, and various other places where Wizards know we players are willing to pay top dollar for them
To be honest, there should be another way of getting Lux out as well, though
Consider that Murderous Cut cannot prevent a creature like Siege Rhino from triggering its ability when it enters the battlefield, it cannot kill a Planeswalker, and it cannot stop an instant or sorcery
Shipping Times We also have the best turnaround in the industry