The free plane cost 400 million to outfit. They didn't put in the anti missile, it's got less than enough backup power, and it doesn't have a lower level escape/panic room/ballroom like the ones Boeing is making both will have. It wasn't supposed to fly internationally but Trump insisted. The 400 million is just admitted, Trump has been diverting funds from a nuclear upgrade fund for months now, nobody knows how much he's actually used on the plane.
And then it turns out this plane is different from the other ones so they had to buy hundreds of millions in equipment to train the pilots who fly it
Add it all up and it's likely pushing 1 billion already. And now it turns out we can't use it internationally.