If your bike weighs less than 10 kg, you probably can't spend your way to a bike that is enough lighter to make much difference. Aerodynamic drag is usually a bigger factor than the mass you are moving anyway. But on a hilly course, weight can make the difference between staying with the pack or getting dropped. Sure, it's not the peloton of Le Tour, but getting dropped still means you'll have to either catch up or find somebody else to paceline with on the next flat bit.
So weight matters. If you can't take it out of the vehicle, then it has to come out of the engine. So far, since the new year, I've dropped my weight by about half my bike weight while adding strength. That was my goal. I have a lot of hills to climb this year.