The Gaming Box RX 580 8G Graphic Card eGPU by Gigabyte has the same graphics card as Apple's Blackmagic eGPU, but costs $200 less.
As its name implies, Gigabyte's $500 Gaming Box RX 580 8G Graphic Card eGPU comes with an AMD Radeon RX580, the exact same card you'd find in the $700 Blackmagic eGPU.
In all fairness, I haven't tried either the Blackmagic eGPU or Gigabyte's own eGPU. Still, I can't imagine that Blackmagic's model includes $200 worth of extras that make it worth buying over Gigabyte's.
And if you want better performance than the Blackmagic eGPU, there's the $615 Aorus GTX 1070 Gaming Box, also by Gigabyte.
The $615 Gigabyte AORUS GTX 1070 Gaming Box comes with Nvidia's GTX 1070 graphics card, which is more powerful than the graphics card in the Blackmagic eGPU sold by Apple. That's $85 less for better performance.
And for significantly better performance for the same price as the Blackmagic eGPU, there's the Gigabyte Aorus GTX 1080 Gaming Box.
The $700 Gigabyte Aorus GTX 1080 Gaming Box comes with NVidia's GTX 1080 graphics card, which is better than the GTX 1070, and significantly better than AMD's Radeon RX580 for the same price as the Blackmagic eGPU.
Alternatively, you could always buy an eGPU enclosure and graphics card of your choice separately.
You could buy a eGPU enclosure on its own, like the $300 Razer Core, and add whatever graphics card you want, like the $280-$350 Nvidia GTX 1060 below. You'd still get similar power as the Blackmagic eGPU for up to $120 less.
