  Thermodynamics of $z=4$ Ho\v{r}ava-Lifshitz black holes in 3+1 dimensions is
studied in extended phase space. By using the scaling argument we find the
Smarr relation and the first law for the black hole solutions of $z=4$
Ho\v{r}ava-Lifshitz gravity. We find that it is necessary to take into account
the variation of dimensionful parameters of the theory in the first law. We
find that the reverse isoperimetric inequality can be violated for spherical,
flat, and hyperbolic horizons and in all such cases we have black holes for
which the specific heat at constant pressure and volume are positive. This
provides a counterexample to a recent conjecture stating that black holes
violating the reverse isoperimetric inequality are thermodynamically unstable.
We find for $z=4$ Ho\v{r}ava-Lifshitz black holes with hyperbolic horizons that
there are two critical points: one showing Van der Waals behavior, the other
reverse Van der Waals behavior.
