I would think it depends on how heavy the bicycle is to begin with, and how much weight is actually being taken off.

The bottles on your back are heavy with water and when you take them off you feel a big difference. But if you were only carrying a vial of water in your back jersey pocket, how much difference would you notice? Enough to pay an extra $1000 to lose it?

Some people might notice that vial and be willing to upgrade to get it off their back. Others wouldn't know it was there even if somebody removed it so they could compare the before and after.

(This is all purely conjecture. I don't do numbers and I'm not even a good rider. Yet!)