how do i manipulate my object with its own properties

Currently learning JS, im a beginner.
I created an object to tinker with, and i want to give it some properties that are dependent on th previous properties of the same object.

I have managed to solve it by working about it yet, i know, i am sure there is a way to do it with in the object definition.

please help me, as a beginner i don’t know what key words to used when googling so this is my best bet.

By doing this :

airMax1 = {
    price : 200,
    appreciation : 8,
    taxRate : 0.2,
    realPrice : ((this.price+this.appreciation)*this.taxRate)+this.price+this.appreciation,
}
console.log(airMax1)

console.log(airMax1.realPrice)

i was expecting this output :

{ price: 200, appreciation: 8, taxRate: 0.2, realPrice: 249.6 } 249.6

yet what i get is this :

{ price: 200, appreciation: 8, taxRate: 0.2, realPrice: NaN }
NaN

but when i do it differently like this :

airMax1 = {
    price : 200,
    appreciation : 8,
    taxRate : 0.2,
}

airMax1.realPrice=((airMax1.price+airMax1.appreciation)*airMax1.taxRate)+airMax1.price+airMax1.appreciation

console.log(airMax1)

console.log(airMax1.realPrice)

it works and gives me the disered output of

{ price: 200, appreciation: 8, taxRate: 0.2, realPrice: 249.6 }
249.6

how can the same math formula produce a number when its outside the object and not produce a number when its inside the object.

i have swapped the object name with the this. method and all