javascript – Improving or replacing a long if statement

I have a an if statement that works just fine, however, it has become a bit long and I need help to figure out how I can reduce the lines of code and thereby the readability.

I have a defaultMonth and set of months and a corresponding price. I need to add or reduce the price depending on the defaultMonth and month selected by the user.

Here are some examples of the output I need (note the interval is the same):

If default month is 60 – set price accordingly:

Month    -     Price
60             0.0
48             0.1
36             0.2
24             0.35
12             0.5

If default month is 48 – set price accordingly:

Month    -     Price
60             -0.1
48             0.0
36             0.1
24             0.25
12             0.4

If default month is 36 – set price accordingly:

Month    -     Price
60             -0.2
48             -0.1
36             0.0
24             0.15
12             0.3

The way I’ve built it now is with an if statement for each default month and nested ifs for each month.

if (defaultMonth === 60) {
    if (month === 60) {
        this.price += 0.0
    }
    if (month === 48) {
        this.price += 0.1
    }
    if (month === 36) {
        this.price += 0.2
    }
    if (month === 24) {
        this.price += 0.35
    }
    if (month === 12) {
        this.price += 0.5
    }
}
if (defaultMonth === 48) {
    if (month === 60) {
        this.price -= 0.1
    }
    if (month === 48) {
        this.price += 0.0
    }
    if (month === 36) {
        this.price += 0.1
    }
    if (month === 24) {
        this.price += 0.25
    }
    if (month === 12) {
        this.price += 0.4
    }
}
if (defaultMonth === 36) {
    if (month === 60) {
        this.price -= 0.2
    }
    if (month === 48) {
        this.price -= 0.1
    }
    if (month === 36) {
        this.price += 0.0
    }
    if (month === 24) {
        this.price += 0.15
    }
    if (month === 12) {
        this.price += 0.3
    }
}
if (defaultMonth === 24) {
    if (month === 60) {
        this.price -= 0.35
    }
    if (month === 48) {
        this.price -= 0.25
    }
    if (month === 36) {
        this.price -= 0.15
    }
    if (month === 24) {
        this.price += 0.0
    }
    if (month === 12) {
        this.price += 0.15
    }
}
if (defaultMonth === 12) {
    if (month === 60) {
        this.price -= 0.5
    }
    if (month === 48) {
        this.price -= 0.4
    }
    if (month === 36) {
        this.price -= 0.3
    }
    if (month === 24) {
        this.price -= 0.15
    }
    if (month === 12) {
        this.price += 0.0
    }
}