Artist's conundrum

The library is going to show some of my photographs in their gallery throughout the month of Janury.  I asked them if they'd let me display my Imaginary Portraits paintings and they said yes.  Now, they also asked me to put prices on everything and give the library 15% of whatever I take in.  For the photographs, I don't care at all! It's all digital printsso I'm never actually losing anything; I can print infinite copies of the photos.  But the idea of handing over one of my paintings is a different story.  I made them just for my own artistic expression.  I think they look great on my wall and I'm proud of them.  I could always replicate them to an extent, but they're truly one of a kind because of the imperfections and unpredictability of watercolor and my own unprofessional hand.  
I can't even fathom Dali painting something like Persistence of Memory and then selling it.  But I guess that's what makes a professional artist.  I never set out to be a professional artist, but the idea of someone I don't know looking at my work and saying "I'll pay you for the privilege of owing that " is pretty damn enticing.
So what do I do?  Sell my paintings for a high enough price that most people won't buy it but those who do give me enough to assuage my personal attachment? Do I sell them for a reasonable amount to get my work out there and try to build a reputation? Do I not sell them at all?
Am I such a true artist that I created the paintings for the sole purpose of creating?  Well, yeah.  Does that make me more of artist than one who lives solely from selling their art? These are questions I never thought I'd ask.  
I'd be grateful for any advice anyone has to offer.