Jaimie, I very much doubt that 1st class is double the economy class.
I haven't checked recently but from my travelling days but it's far far more than double economy on long haul.

I reckon it's more like 10 times the cheap economy ticket with business class maybe 3 times cost. I just guessing quickly.

Whether it's worth it is completely relative to your funding.
When I travelled for business anything over 10 hours could be booked first class at my level.
I did it many times without any concern. Wonderful.
Well worth it for me.

It's relative. I reckon you pay 5 or 6 grand for a first class flight to Manila.
How does that stand with you if it's from your own bank.
Me NO WAY ON THIS EARTH