I've listed a few areas that can genuinely impact how a frame performs.
All those lines and curves aren't just for show, they all contribute to the function of the frame. NACA profiles, kamm tails and squoval tubes are just the start but most definitely contribute to a frame's characterstic beyond just appearance. Designed for comfort, stiffness or aerodynamic effect its the small details that can have a big impact on performance.
Metal bike are generally welded together but even then things like butting and hydroforming play a role in the end user experience. When it comes to carbon bikes all frames are definitely not created in the same way. It might be bonded tubes, lugged tubes, monocoque molds or multiple individual pieces. Cost certainly plays a part here but it's not the only factor. Ride quality and characteristics can be tuned through construction methods alone.
Steel, alloy, Titanium, carbon (bamboo is a little niche for our tastes). The metal bike industry is very much in the shadow of carbon fibre but shouldn't be ignored. They definitely have their place. Carbon frmes are definitely not created equally. Different carbons, and there are a lot of them, give different ride qualities while the addition of materials such as elastomers, various resins and graphene are added for various reasons but are becoming more common place.
Probably what most performance orientated cyclists are interested in, rightly so in our eyes. Our sport is generally about going fast but so many factors contribute to this. We aren't aerodynamacists but we understand enough to help. We aim to cut through all the marketing and give verifable, independantly tested receommendations so if you want a fast race bike you can be sure that is exactly what you are getting.
I'm not sure anyone has gone into a bike shop and asked for the heaviest bike they have. We all want a light bike, dragging extra grams up hill and down dale isn't anybodies idea of fun. There is a point where lightness becomes a compromise, however that point is most definitely rider specific. Claimed weights are rarely accurate as the manufacturers use all kinds of caveats to hit a certain mark on the scales. For example, that really light frame you just read about was actually weighed without paint but you can't buy the frame unpainted. You get the point...
So in summary, there are a bucket load of factors designed into each frame that will affect the ride quality and characteristics. Getting the right one for you is our job, riding and enjoying it is yours.