When I was tank-shopping a month or two ago, and trying to decide between a 75g, a 90g, and a 120g, I found the 120 was substantially more expensive (much more than the price difference between the 75 and 90). The fact that it had 2 overflows instead of just 1 like the 75 and 90 may have been a factor. I don't remember the exact pricing, but I think the 75 was about $250, the 90 around $300, and the 120 was close to $500.
90g AGA Reef-Ready; 20g sump; 12g refugium; ASM G2 skimmer; 2x Maxijet 1200; Quiet One 3000 return pump
2 Ocellaris Clowns; Nassarius, Cerith and Strombus snails; Scarlet, Blue-Leg, and Zebra hermits.