  The scaling physics of quantum Hall transport in optimized topological
insulators with a plateau precision of ~1/1000 e2/h is considered. Two
exponential scaling regimes are observed in temperature-dependent transport
dissipation, one of which accords with thermal activation behavior with a gap
of 2.8 meV (> 20 K), the other being attributed to variable range hopping (1-20
K). Magnetic field-driven plateau-to-plateau transition gives scaling relations
of (dR$_{xy}$/dB)$^{max}$ \propto T$^{-\kappa}$ and \DeltaB$^{-1}$ \propto
T$^{-\kappa}$ with a consistent exponent of \kappa ~ 0.2, which is half the
universal value for a conventional two-dimensional electron gas. This is
evidence of percolation assisted by quantum tunneling, and reveals the
dominance of electron-electron interaction of the topological surface states.
