Not sure why the ClearSonic hinge is so special, but TAP Plastics sells their Flex-fold 2 hinge for ~$15 that lasts well over 2 million cycles.
I built a 1/4" thick 2-panel that is taller and wider than the ClearSonic for about $120. If I did it again, I'd buy the TAP hinge and be done constructing it in 30 minutes with less hassle and cost than a piano hinge. That said, if I were a company, I probably wouldn't sell something like Joe's for much less than ClearSonic is. Got major overhead to cover. DIY is almost always cheaper - no profit margin reqd.
Guitars: '79 LP Custom, '01 Dickey Betts Goldie - 80 of 114, '00 Chandler Lectraslide
Amps: '00 Marshall 1987x, '70 Marshall 1959 SL, 4x12 JBL D120s
'64 Vibroverb - JBL D130, '66 Super Reverb - CTS Alnicos
'77 Peavey Deuce (great for melting stubborn ear wax)