Yep, eGPU prices are dropping fast. Razer was first at $499, now we're at $379. "Right price" for mass adoption is probably around $300.
Macbook Pros being announced this week will have TB3 too, and rumors are that Apple will release a new 5k monitor with an integrated GPU. It took a full year more than I hoped, but external GPUs are on the cusp of becoming mainstream.