I have had 3 inexpensive scales recently, all purchased for around $30 from eBay. All worked well for my purposes, which not only includes cooking, but also I spin yarn, raising angora rabbits for that purpose. I've weighed everything from exactly 10 grams of fiber to a 10 lb box going to the mill to be spun and found each of the scales to be very accurate. If you can believe UPS's scales as a standard, my 10 lb box (actually more than that, it was 10 lbs of fiber, but the filled box weighed more, of course.) - only differed from the UPS scale by a few grams.
When I weighed out an ounce of yarn, to estimate how much in pounds I needed to cover a certain # of square inches of fabric from a small square, the finished project only differed from my estimate by less than an ½ ounce. (I was a math major, so figuring out the curves was not difficult for me.)
So I say either I've been extraordinarily lucky, or most scales are pretty accurate.
(BTW, I dropped the 1st one and broke it. the 2nd one was never returned to me, and I now have the 3rd one.)
Thanks a lot for sharing all these features to check out while buying food scale. It is very useful information. Thank you.