Why the massive price difference between 120 and 135 pro slide films
Apologies for cross posting but I tagged this question on to a comment about slide film in the Fotokemika thread in the B&W forum and I recognise that it was the wrong place to ask.
Anyway, why the ridiculous difference in price between pro slide film in 135 and 120 format? Provia 400x is somewhere between £5-£6 per roll in 120 (from a pro-pack) and over £10 in 135. Provia 100f is available for £3.20 per roll in 120 (from a pro-pack), but £8.39 for 135! It is roughly the same film surface area and generally I guess 135 sells more, so production of canisters and packing material can't account for it. Also Fuji make the AgfaPhoto CT Precisa film, which is apparently a slightly modified version of Provia 100f, so they clearly can produce cheap 135 slide film.
I guess the answer is to shoot the Agfaphoto film, if I want cheap slides in 135 format, but that means nothing like Velvia when it comes to landscapes.
Does anyone know of a good reason for this, or are Fuji trying to kill slide film as a consumer product?