Those prices are in Canada . It doesn't matter where you buy your film, if you punch in the prices from B&H you get the same scenario with Kodak. TMX is $1.65/sheet while Porta is $3.50/sheet. Whereas the 120 rolls are $4.50 and $5.09 respectively. Why the huge difference in sheet film?
Interestingly enough Fuji prices don't show that same trend. It's a Kodak thing.