I'd think you'd want a digital model for that kind of money.

Digital scales need a precise weight (usually a separate purchase) to be calibrated properly. Analog scales just have a knob to turn to adjust it.

Also, 'for that kind of money'? Its $20, not $50 or higher.

What about using 1 liter of water (1KG) or one pound of sugar to calibrate a small scale. Never heard about buying a weight for a scale unless is for a laboratory precision, and then you are willing to spend big bucks for a scale.

perfect for anorexics! Measure in *and* out!

Nice bowl design so you wont spill your yayo.

agreed with #3. I have cheap digital scale ($15 or something). I just use a pint of water to make sure its on... and it is always within 1/8 oz. Good enough since I'm not using it for chemistry or anything.

#2, a knob does not calibrate it, it only zeros it and it may still be off.

#3, what about the weight of the container holding that water or sugar? How do you really know the pound of sugar is exactly a pound until you weigh it with a calibrated scale?

I agree a basic kitchen scale doesn't need utmost precision, but being 7 pounds it could make sense to make sure it's accurate as you might often be weighing things that are mere ounces instead of pounds.

#7 the container you are going to use to hold the water can be the container to use for using the scale later on. So that can be "zero" it out.
(TIP: If you use containers in scales is good to write on them their empty weight with permanent marker, this is what they do in materials labs.)
If you buy 1 pound of sugar (or anything) it should weight around one pound (unless you are getting ripped off)... so the precision should be good enough for baking/cooking.
If you want to get crazy then you will have to adjust your weight for atmospheric pressure, ambient temperature, altitude and use an ASTM calibration procedure, but again we are talking about cheap scales for home use.