If you rent a render farm it can be cheaper but not everyone can have access to super fast internet to produce complex CGI and 3D models. Render also farms work better with more hardware/processing power in the end. So it's down to a cost/performance/time ratio.
As for the Radeon Pro Dueo...
The Radeon Pro Duo is meant for 3D design and creation, it's a direct competitor to the Nvidia Quatro series. Which can go into the $5000 price range.
Forgive me I know very little about 3D design, but as a crude comparison; The Nvidia Quatro P4000 comes it at the same price of around $1000, it has 243 GB/s Memory Bandwidth where the Radeon has double at 448 GB/s. (The Titan Xp does around 547.7 GB/s at $1200) Additionally the Radeon is ​11.45 TFLOPS in compute performance, where Nvidia is around 5.3 TFLOPS. Double the performance at the same price.