I discovered that you can order ink samples from The Goulet Pen Company so I decided to give it a try. The cost for the samples depend on the ink that you choose. However, I found the prices to be reasonable.
As you can see from the photo, I ordered a variety of turquoise and blue shades. I like the idea that the samples allow you to test out the ink before purchasing a full bottle. I haven't decided on my favorites yet. I plan to use the samples for pen & ink sketches.
The company also offers a Ink Drop Club that is on hiatus until December. "The cost is $10 per month (or $15 per month outside the U.S.). You receive 5 fountain pen ink samples as well as access to a special club page with extra discounts and promotions."
I have no relationship with the company. I was just satisfied with the samples that I purchased.