As with my other materials, you are free to use the "Print and Go" activity and share with others. My intent has always been not to add a price tag to my resources, but with the increase in cost in making them, I have decided to place the answer keys up for sale on TpT. My idea is that you take what you need, when you need it without worrying about cost (i.e. when you get a call that you need to pick up your kid from daycare, or you wake up with a migraine - you get the idea). Later, you may wish to pay it back. Even if you use them all and you just purchase one answer key, it would definitely brighten my day.
Update: Except for the ones that include graphs, the answer keys also include access to editable versions.
Disclaimer: The colors you see in the thumbnails and on the first pages of the free downloads have been scrambled / do not correspond to the correct answers. This was done in order to prevent students finding this page and simply copying what they see.