I would assume that the time the manufacturer states would usually be per frame/image. But maybe more important to know is that the time stated often is without applying any settings to the image. And applying settings can increase the time considerably. Making a preview first also adds up.
In general I find scanning is very time consuming. I have used a Nikon Coolscan V for a couple of years, and with that particular scanner I usually scan 4-7 images per hour when applying settings and doing adjustments in the scanner program (Nikon Scan). If I only do minor adjustments I scan up to 10-12 images per hour.
I have recently started using an Epson V750, but I have only scanned a few images until now, so I haven't had the chance to compare the scanning times with my old results, which was done with another PC.