According to ToyFare's Price Guide (all prices listed in USD, MISB/MOSC LM):

Soundwave & Buzzsaw = 345 155
Frenzy & Laserbeak (metal feet) = 85 20
Rumble & Ravage (metal feet) = 105 25
Frenzy & Ratbat (gold weapons) = 75 16
Frenzy & Ratbat (silver weapons) = 55 15
Frenzy & Ratbat (painted details) = 60 18
Slugfest & Overkill = 55 7
Beastbox & Squawktalk = 85 35

Eject & Ramhorn (gold weapons) = 65 15
Eject & Ramhorn (silver weapons) = 70 18
Rewind & Steeljaw (gold weapons) = 52 15
Rewind & Steeljaw (silver weapons) = 65 18
Grandslam & Raindance = 75 24