Both storage types will have comparable prices at 128GB, and their cost per GB will decrese at different rates as you increase storage capacity. It's not fair to compare pricing between different storage capacities across different storage types, that is why I have shared 1TB drives from the same vendor.
Also, a cheap 128GB SSD is way less than the price you have suggested, even a 120GB Kingston SSD is only $20.
https://www.amazon.com/Kingston-120GB-Solid-SA400S37-120G/dp...
120GB SSDs are $20 https://www.amazon.com/gp/product/B077ZK1FJF/
A cheap 128GB SSD would be around $40-50 while you can get 3TB HDDs for that price.