What I found though a Google search is that the SHM CDs only differ from regular CDs in their enhanced transparency polycarbonate on the read side of the CD.
They may sound better than regular CDs, but how much more can "enhanced transparency polycarbonate" cost than the plastic used in standard CDs to warrant their $28 cost?
In other words, it seems to me like a marketing twist to sell more back catalog product without a significant materials outlay.
$28 per SHM CD?
I think I'll buy more $10 SACDs...
IMO...