I can tell you that on my worst balanced rods (long, heavy sticks) that I have added butt caps and weights to to balance them, while you end up getting the desired balance, you can definitely feel the effect of having the added weight on the back end of the rod when you cast. Additionally, since most casts aren't simply wrist rotation, but also involve some arm movement, the momentum/inertia feeling just made things seem really awkward for me. Add in the loss of sensitivity, and I have since removed and stopped using any of the aftermarket add-ons for rod balancing.
You are correct that the longest rods I own (7'3"-7'6") have the "worst" balance (relatively speaking), but not so much on the price point aspect. My best balancing spinning rods range from 6'2" - 7'0", and have a price range between $49 (Berkley Lightning Rod) and $270 (Loomis & Custom builds). My best casting rods range from 6'0"-7'0" and have a price range from $40 (Lightning Rod, again) to $230 (Loomis).
On the balance point, if you start with just a rod blank and give it to two different builders/manufacturers, you can end up with two very different balance points for the same rod based on the components used and things such as guide number and spacing, materials, reel seats, butt length, etc., etc., so I would say you can have a big effect on that balance point, which goes back to my point of the best balanced rods are already built toward that end.
By measuring several parameters of all the rods I own, I have come up with a formula that lets me know pretty well how balanced a rod will be before I even buy it, assuming I can get those parameter measurements in advance. Not too difficult in a store, but much more challenging if buying online. It works for me... and things like reel weight and lure weight don't seem to play as big a role as some might think.