What is the average pay per hour for UE4 freelancers?

Not really.

The hourly rate depends on the turn around time and is not really intended for over the counter products and is usually an amortized cost of being able to do bread and butter work much quicker at much higher level of quality as compared to someone who does not have the skill level to complete the same task in the same amount of time, (AKA false economics).

As the client though you do have the right to see a portfolio of their past work and ask for the turn around time of X element that you like which is usually less than what it would cost you based on an hourly rate.

As always it’s about knowing what you are buying.