I agree with C. and J. There was a kid in the buy/sell forum... he'd worked his ass off on a 1980's qt-50.... mods, restoration, everything....
he expected that since he'd 'invested' so much, other people would pay him for it....
it was tough convincing him that no matter how many hours he put into it... blood sweat and tears.... it didn't affect the cost at all.
Keep it... or sell it to a friend for a good price.
what year is it? mileage? what in the heck was so bad it took 300 hours to fix? that's almost 13 straight days of work, round the clock, 24/7
good luck though. I've never seen a Beta moped. I ought to go check the pictures section.