My understanding is that MP3 compressed to 320kbps is generally considered to be the equal of WAV then - I have a mix I initially exported as WAV @ 723,413 MB which is about 1 hr 10 mins long.

When exported as MP3 (320kbps) this amounted to 131,233 MB.  If my memory is correct about the compression level of the MP3 in question (its possible I exported it as 256 kbps) then by the same ratio 600 GB of WAV files could be stored as 108.84 GB of MP3 320 kbps.