This goes against the "single source of state" principle, but if computations on a prop are expensive you can cache them on the component. Instead of directly using doExpensiveComputation(this.prop.someProp) in the render method, we can wrap the call that caches the value if the prop is unchanged

cached_computation.js

getCachedExpensiveComputation() {
  if (this._cachedSomeProp !== this.prop.someProp) {
    this._cachedSomeProp = this.prop.someProp;
    this._cachedComputation = doExpensiveComputation(this.prop.someProp);
  }
  return this._cachedComputation;
}