Velvia 50

So Velvia 50 hasn't been manufactured for a while due to a required
component being unavailable. And most, if not all, stores have run out
of it in 135 format. However it seems it's still fairly available at
120 format - is this just because 120 format film stock moves slower
or is this version still actually being manufactured? I bought some
rolls last month without noticing the 135 format version was gone -
and now when doing eBay searches, there's a lot of it in 120 format
with reasonable prices, and smaller amounts in 135 format with a
relatively high going price.
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