Even if I won the lottery £65+ million I would never spend that kind of money on a bike, even if the half centimetre was a physically gain
That's your choice and a 100% valid one but the OP's choice to buy a top flight machine is his, equally valid and he doesn't need any further 'justification' than he wanted to because he likes it. We shouldn't belittle other's choices and dictate how they spend their disposable income. It's no different to someone wanting a Bugatti instead of a Kia. If they can afford it, it is their money and if makes them happy, great. I dislike alcohol but I'm not going to diss someone for spending a fortune on fine wine or whiskey.
As for the gains high end bikes can deliver, they are tangible. Marginal yes, even more so when ridden by someone who is not in peak physical condition and who would not realise the difference or doesn't chase fractions in time. I have taken two overall KOM's this week on my Madone that I repeatedly failed to do on my Wilier - which has helped me to over 70 since August last year. Now, the difference is aero vs light-weight in this case, the aero bike proving faster in the sprint for me. A matter of seconds. Nothing of any importance to anyone not interested in marginal gains, of course. We are the engines that provide the power, sure, but different bikes can help us achieve greater speed and/or endurance. I'd suggest a £1500 bike will deliver the most in terms of quality vs performance for most but if you are physically at the top of your game and striving for more, marginal gains may be important to you. We all have different goals and enjoy the common interest in cycling in different ways.
