Why?

I can afford a Time with full on Dura Ace DI 2 and all the bells and whistles. And IMHO, that is absolutely the best bike on the market today. 10k +/-

I choose to ride a 2k bike with an aluminum frame and 105. We are talking an 8k differential in price.

Would the Time last longer? Will the Dura Ace last longer, be more durable than the 105? No.

The overwhelming majority of cyclists are not racers, not chasing KOM's, not really concerned with being the best at their local club ride - so what does that 8k really do? Nothing.

What would be the justification, other than "I want it" (which is valid) for simply buying the most expensive thing you can?

How bout - buy a bike that fits well, with a level of parts that perform and last for 10-20-30k miles++, and don't simply spend crazy money on parts that in the end, wont really do anything for you?

Want vs need. Nothing at all wrong with the want - but it;s not what people need.