This is the crux of the question. Why do you want the thing? If it's about having "the best", and there is nothing wrong with that, and you believe that the Pinarello is "the best" then nothing else will do. That's the value of a brand. If I'm driving a Ferrari I don't care if some Japanese turbomobile may be faster, it's not important. I'm the one in a Ferrari. If it's about performance, and you reckon that the Lapierre performs the same, or possibly even better with nicer wheels or tyres, then that might swing it for you. We all know the limiting factor is the engine, and Julien Alaphilippe will be faster on my £800, 15 year old
Decathlon bike than I would be on his. I'm not even convinced that I'd be quicker on his bike than mine. But if I had the bike of my dreams, and every time I saw it I went "wow" and wanted to ride it, then that's worth your £x thousand. If every minute on it is a joy because you are on "the best", then that makes it worthwhile.