I own all three scales that Harbor Freight sells. The 500 and 1000 gram models were $10 each, the 5000gm was $19, all on sale.
I don't have a calibration weight so I weigh parts on more than one when I can and they usually read exactly the same.
Just to get a rough figure, I weighed my new bike with my digital bathroom scale; me holding bike minus me without bike. I'll check that number with the hanging scale at my LBS.