I've experienced the pros & cons of both approaches. Here are some things I've learned:
Owning the Only-- Few customers love an OOAK creation enough to pay significantly more for it.
Creative Flexibility-- The artist's imagination has total control when creating OOAK inventory. It's fun!
Balancing the Challenge-- ...BUT if the joy of creating OOAK isn't balanced by marketability, prepare to be another Starving Artist:) Also, creating multiples of one's most popular designs is a great Plan B when the creative well runs dry.
Wholesale-- Shops & pricey boutiques may buy a selection from OOAK artists initially. But they'll often followup with requests for multiples of the best selling ones, perhaps in different sizes & colors. To support such a market, consider removing the OOAK label.
Creating Multiples-- Each iteration of the item becomes easier to make. Hopefully that results in more profit as labor becomes more efficient. However, the process gets boring & might feel like the opposite of creativity.
SPECIAL CHALLENGE: Creating Custom Multiples for ONE Customer
Given ONE well-made custom item that meets specs, the customer will likely LOVE it. BUT delivering well-made custom MULTIPLES to a customer is riskier. Because each handmade item will be slightly different, she'll probably prefer ONE & wish all of them looked "exactly" like that one! The more particular the customer is up front, the more likely she'll find a Pick of the Litter & love the others less. It's human nature, even though the artist explains the certainty of differences before taking the job. Hopefully the customer can become happy with the unique beauty of each multiple:)
I have as many questions as answers about these practical aspects of creating art & hope you'll Comment with your own experiences. I'm learning the ropes in the School of Trial and Error. "T & E" is a tough school!