Over here the GS pro kit is about £400 or $720 approx. If I were to do the Mugen truggy I would have to get the MBX5 to convert which is about £500 or $900 and then get the conversion kit, which will be another £150 or $270 at least.
The Hyper kit and the Kyosho would be cheaper than the Mugen but when you add it up the GS saves you a bit and is ready to go as soon as you put the engine and electrics in it, which I already have. I was going to get the GS initially instead of the HPI and although I don't regret buying the Savage, with hindsight I would have done thing differently and saved a bundle!! Ah well, you live and learn!