Caulifower is special situatiuon this month due to the cold weather, but also some blame being laid on LC and Paleo types...like you Noticed even in Sweden:

http://www.dietdoctor.com/theres-a-...rices-skyrocket

I laid in some frozen cauliflower bags before the holidays (Walmart Great Value brand) and haven't noticed if their supply/price has also been affected since then.
I find frozen is fine for mashed fauxtatoes, other recipes you may see the taste difference.