If your not talking about upgrades to Business or First with points but actually paying money for the tickets, i'm in a situation where i can afford business and first class sometimes

But i do find it hard to justify the extra cost and often will fly economy

The bottom line is even in the very nicest first class, your still stuck in a restricted space for a period of time, yes it's a bit nicer restricted space, but it's not like your getting full body massages with happy endings and watching tv on 100 inch screens with DTS X surround sound. Often your asleep for a large amount of the flight anyway

I just prefer to spend money on nicer hotel rooms/more expensive entertainment options at your chosen destination

If your rich enough that a first class ticket means as much to you as losing 5 cents means to the average person, then fair enough. I'm not quite at that point yet