I know so many people who have had the same experience as you! I find fine arts culture (painting, sculpting, drawing, etc.) often have an anti-commerce perspective, while design culture (illustration, graphic design, etc.) tend to have a far more business perspective. There are exceptions for both, of course. As it was mentioned, some smart art schools make this sort of thing required. Marketing, public speaking, accounting, branding, and law (contracts and copyright specifically) are all topics I wish my school taught - we didn't have ONE business class, and boy was I sore about that. Luckily I had a marketing major before art school, but I still got so frustrated when my classmates struggled. And I would have LOVED to learn many of those things through an artists perspective.
I went to a workshop and met this lawyer, Katie, who lives in Portland and she was AMAZING at teaching the dryer stuff for artists. Look on her website, as I believe she does workshops at conventions and things. The Right Brain Business Plan is another resource to look into, as it too goes into budgeting, business, and numbers but through an artists perspective. There are also several online courses for artists in business, but they cost $$$! Drawn and Drafted Art Business Bootcamp was one such course I bought (affiliated with Kyle T. Webster, that guy who does the amazing Photoshop brushes), but I haven't had a chance to go through it all yet. Looks good though, if you have some money to spend! There are so many free resources out there too, they just aren't wrapped up in a convenient little package for you. Finally, this book is important if you are freelancing and such, as it goes into contracts and pricing, and I reference it every time I take a new job or to get an idea of what to expect as an artist.
This might not be what you're looking for, but they've helped me out. And you are so right, selling a rock is brilliant! Selling what people want isn't selling out (unless it's destroying your soul), but many artists still don't understand that.