Bowl blanks and turning blanks are often coated with wax. If you are turning a bowl, then the turning tools will remove the wax as you go. Often people turn a bowl to rough shape, then leave it sit on the shelf for a year where it may warp somewhat while it rests and dries thoroughly. After that, they chuck it up again and finish the bowl to its final shape and thinness. After 25 years, I wonder if this step is necessary for your bowl blank.
If you are not going to use the wood for turning, then you can remove the wax through trimming or scraping or whatever. Sandpaper will not work. It will gum up with wax before it does much good. In theory, you could dissolve the wax with a chemical like mineral spirits, but it would be messy and not worth the effort.
A moisture meter will tell you more about the wood's readiness than any amount of text I can write.
Unless the wood is damaged or has visible flaws, $50 is an excellent value for a 12x12x9 maple bowl blank. It may have a hidden flaw on the inside, but that's an aspect of woodworking life that we all share.