different issues here: cost, weight, durability, etc.
OP asked if there really is a difference in graphite rods? Imho, yes. Then mentioned "really expensive ones"... I think the best of the middle ground is better for most fishing trips.
there is a lot of room between basic and megabuck. imho, some new rods that cast very well are mid-priced and a bit heavy, not expensive and superlight. echo carbon.
my 7'3" echo carbon two weight weighs three ounces, versus the two-ounce weight of my mystic 7'3" two weight. the echo was recently out there as a $125 closeout, mystic would be twice as much. echo is an 8, mystic is a 10 (a 2pc wonder for my trips for spooky wild browns on dries).
I once broke an echo carbon tip by hitting a branch with the last few inches of the rod in mid cast. they charged me $35.
I fish a lot and would rather use a rod that is more enjoyable to cast, plus with the downright scary accuracy of an echo carbon I should catch more fish.
PA trout arent going to break rods very often. I am something of an expert at putting flies in trees, and have never broken a rod tip pulling one out with any fly rod... (knot leader or fly has to be weak link, not rod tip... worst case, point the rod at the fly before you pull so the rod isnt stressed)
if you look up the fly fish ohio great two weight shootout, one reviewer summarized the echo 2:
"The rod handled the DT2 and the WF3 equally well. Fly size didn't seem to matter (within reason) and the outfit was accurate to a fault. In my notes I wrote "I feel everything about the cast and can do tricks - amazing reach and puddle casts, awesome change-of-direction casts and very, very good roll casts to whatever distance I need." I went on to say "If you aren't delivering the fly with delicacy and precision, it's you and not the rod." This stick has great fish feel, but I felt it to be just a touch soft in that last bit of butt strength. I noted "good choice for small trout or bigger fish on calm waters." Finally, my last sentence in my casting notes simply said "I love this fly rod."
I agree, that is very much my experience, and the echo was $170 msrp before the $125 closeouts... I also have a 7'6" echo 3w, great caster as well.