Excessive as cost might be, if broadcaster under influence of a drug? (3-4)
I believe the answer is:
sky-high
'excessive as cost might be' is the definition.
(excessive costs might be said to be sky-high)
'broadcaster under influence of a drug?' is the wordplay.
'broadcaster' becomes 'sky' (Sky is a television company).
'under influence of a drug?' becomes 'high' (high can mean using drugs).
'sky'+'high'='SKY-HIGH'
'if' is the link.
(Other definitions for sky-high that I've seen before include "At an excessive level" , "Very pricey!" , "Very elevated" , "At great altitude" , "such costs are very steep" .)