Heli-max is a Great Planes brand. As stated, they only re-brand and re-distribute the helicopter. It's actually made by ARK Taiwan. It's more expensive than the X-400 kit because you pay for the name and, to an extent, support. I'd imagine replacement parts for the x-400 would be cheaper in comparison aswell compared to buying them under the MX400 name.

As for your problem, well, gunning the throttle breaks things. It's not an MX400 specific problem. Most helicopters will sustain damage if you jump the gears when the main blades aren't atleast rotating. Learn from your mistake and engage throttle lock from now on when adjusting things on your helicopter or transmitter. I won't do anything on my heli unless throttle lock is engaged.