How much is down to the bike?

My tuppence worth. Its all about weight, I have an aluminum winter bike thats adorned with all sorts of gubbins that make it heavier than an anvil.
Its a struggle on a climb of say 2k or more. I also have a boutique carbon bike/carbon hoops which is a revelation, makes me feel like a climber, I am not a climber.I also have a titanium road bike which is similar in that it weighs hee haw.
Point is light bikes make things alot easier because they are lighter. However if you are 15 stone my theory is fucked:)
So yes a more expensive bike makes a difference going uphill because its lighter.

Yes, a lighter bike makes a difference but how much is the difference and is the difference worth the cost?