- 2015 $600: Samsung T1 http://www.thessdreview.com/our-reviews/samsung-portable-ssd...
- 2016 $430: Samsung T3 https://www.storagereview.com/samsung_portable_ssd_t3_review
- 2018 $200: Samsung T5 https://www.androidheadlines.com/2018/12/samsung-t5-portable...
Another incredible exciting point is the amount of competition coming up, it's not just 2-3 large vendors anymore.
If things continue at this pace it seems sensible to expect a 10TB SSD consumer drive for under $1000 within a couple of years.
Note: not afiliated at all, just a happy consumer.