From my very limited experience, I can say from using a similar 6-18x50 Panamax and 4-12x50 mountmaster that there are marked differences in quality, the sharpness, FoV, etched glass retical on the Panamax far surpasses the mountmaster. However despite the obvious quality differences between the mountmaster and the panamax range, it dosnt make the mountmaster a bad scope, I mean seriously I dont have a huge amount of experience but i can quite easily put a very reliable pellet upon pellet with the mountmaster, although a low end scope, at ~£50 the mountmaster more than sufficiently accurate and reliable for me as a "beginner".
TL/DR version
You can quite easily see where the money goes into the more expensive scope, but dont let that take away from what is a good value sight in the mountmaster. But then I guess you could say the same for a lot of expensive sights.