That was crazy, too—last year I saw them get down to the $350 range (almost bought a couple more at that price)... and yesterday when I went to check on them I noticed they're up to $530!
When I bought my drives a couple years ago they were around $400. I wish there were more options for 4-8 TB SSDs that went for capacity over performance. Honestly I would be happy with some larger lower-cost SSDs that ran at 100-200 MB/sec just for silent, low power capacity.