The ROCKET has a 0:1 glide ratio.
It must sustain thrust all the way back to the landing pad.
Additionally, there is significant structural mass added to the vehicle to be able to land.
Refurb and Recycle costs are also significant, as we learned with Shuttle.
It would have been cheaper to throw the SRBs away than the total costs of making them reusable.
It was a political design, not an engineering, cost/benefit design, because the concept of recycling was sexy.
You’re comparing refurb costs of politicized 1970’s technology to the Falcon 9-R? Say what? We’re talking about SpaceX, not the Shuttle.
And in any case you seem to be missing my point. The mass of the landing gear of a 747 may be “significant” too, even if they were made out of carbon fiber and aluminum honeycomb like the F-9R’s landing gear, but the fact that it allows the reuse of a $30-40 million vehicle is more important than the added mass in both cases.
And it’s not actually true that it must sustain thrust all the way to the landing pad. After the three-engine retro burn, the center engine only needs to impart enough delta-V to offset the terminal velocity of the falling, nearly-empty stage close enough to the ground for a soft landing.