Balanzza travel scale for frequent fliers
The new "Balanzza" travel scale is designed to assist travelers by making pre-flight weight checks less of an exercise in surprise. Even better, the press release for the $25 gadget included this handy chart. I updated the information for JetBlue and added Virgin America. If you've any additional airlines to add, I can easily punch them in.
Product Page [Balanzza.com]

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Note that this is actually just a fishing scale - I've got one just like it. But it's not overpriced, so what the heck.
Fish scales quite nicely fill the gap between small things you need to weigh on a precision balance and big things you can just stick on the bathroom scales.
It would be funny if this thing weighed ten pounds.
For Frontier Airlines:
1st bag checked = free
2nd bag checked = $25
50-99 lbs = $75
Over 62 linear inches (Height+Length+Depth)= $75
Yes I know that stuff doesn't fit in your chart right. Also, these prices are effective June 10th. Right now 2 bags can be checked for free. The weights and limitations are the same, except the fee is $50 instead of $75.
Actually, that's one of those mindblowingly useful things that I've never realised I'm lacking.
I tend to pack big toys when I go on holiday (power kites, SCUBA gear, hiking boots) so I'm always left trying to decide which way my bathroom scales' calibration has drifted.