Not as expensive
'not as expensive' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for less that I've seen before include "See 12" , "In smaller quantity" , "more, as they say" , "Minus; not so much" , "Fewer in number" .)
(Other definitions for lower that I've seen before include "Lessen" , "Take down" , "Let or haul down" , "Less high in place or position" , "Let down, being inferior" .)