There should really be no need to be deleting raw originals. The post-processing technology is developing all the time. You would be amazed at what can be recovered in the shadows of old raw data. As an example, it's now technically possible to build a 3d model of an underwater cave by extracting individual frames from old underwater video taken in the early 90s and processing with photogrammetry software.
A 4TB 2.5" external drive is about £90 and the size of a fag packet. A typical raw file is 20mb. That's 200,000 raw files. 22 images stored for 1p.
I think Mark Burkey told me that his entire catalogue of raw images fits in 8TB, including backups.