vf's start around 100 quid +/-
varilux is a brand from essilor who's vf are anything from £150-300+ depending on prescription and the coatings index of lense wanted/needed
the type of frame you choose can also affect the cost as too smalll a frame and you enter the realm of "short corridor" v/f's which again normally cost a bit more and aren't really recommended for a first time user as they are a bit harder to learn to use.
with regard to the 'corridor' mentioned above, Its not the over all depth of frame that is critical, its the measurement from center of pupil to lower rim of frame.If you are looking at either a supra or rimless frame that shows a mil or 2 too short for the v/f an opticians with decent glazing equiptment can usually add that into the lense size.
with all things its a case of you gets what you pays for.