There's this tale of Pablo Picasso I heard awhile back - we'll just say it came from the Internet. It's literally copied everywhere, and even though it's likely fiction, it makes a great point.
Legend has it that Pablo Picasso was sketching in the park when a bold woman approached him.
“It’s you — Picasso, the great artist! Oh, you must sketch my portrait! I insist.”
So Picasso agreed to sketch her. After studying her for a moment, he used a single pencil stroke to create her portrait. He handed the women his work of art.
“It’s perfect!” she gushed. “You managed to capture my essence with one stroke, in one moment. Thank you! How much do I owe you?”
“Five thousand dollars,” the artist replied.
“B-b-but, what?” the woman sputtered. “How could you want so much money for this picture? It only took you a second to draw it!”
To which Picasso responded, “Madame, it took me my entire life.”
Of course, she wasn't paying for the $2 canvas and 1 cent worth of pencil lead, but his experience. It's the same reason we pay more to see a movie with our favorite stars, or a sportsball playoff with our favorite rival teams - the time they've invested pays dividends. An ice sculptor is worth more than his ice, a woodworker more than a dead tree, an artist more than her paintbrush.
I hired an experienced mason to fix my basement wall and paid him more in a few weeks than I make in a few months - not because I can't mix cement and pile bricks and pour gravel, but because there's a level of nuance and experience he has from decades that I can't possibly have. I'm not just paying for materials - I'm paying for his expertise.
So, if you've spent years honing something yourself, you shouldn't feel embarrassed in the least to expect good money for your skills. Sure, open source is fun and has its pros - I have a few side-projects and I'm glad to be giving back. But if you've sacrificed your own finite hours learning something that not everyone can do, there's nothing wrong with accepting payment for that expertise. And if someone seems shocked that what you did was done quickly, remind them that it's taken a lifetime to get to that point.