A 3D artist will charge anywhere from $500 - $2000 for a model when freelancing. This is untextured, unanimated, and without a skeleton. Adding these features often times will increase the cost exponentially, and many times will need to be handled by other artists, as they specialize in a given field - texturing, modeling, animating, rigging, etc…
Now, take into consideration that most of these packs will include at least 5 models, rigged, textured, animated, with the addition of using the Epic skeleton, so that there is some modularity between the free animations released by Epic, and the models you choose the purchase.
Assets are expensive, that’s for certain, but buying from an asset store is infinitely cheaper than working 1:1 with an artist for most cases. And if these prices are still not acceptable, there’s no reason to not pick up some skills and make your own! Gamedevmarket, TurboSquid, and other asset stores might also offer content of the quality you’re looking for, but it most likely won’t work “out of the box” with UE4.