We also went to Butterfly Farm, but did it on our own. By the end of the day, the cost was probably only slightly less than the Disney Excursion. What we really liked was that we were able to go on our own schedule.
We took a cab to Butterfly Farm, and arrived just after the
DCL excursion folks were processed, and were told to join their group for the tour of the Farm. After the tour, sweet drinks were offered to all, then you go back in to explore some more. It seemed it was only a few more minutes when the DCL excursion folks needed to leave. We stayed for a while longer and had a great time exploring and trying to get the Butterflies to land on our fingers.
The cab was a fifteen passenger van, which we shared with a group from another cruise who who were going to Orient Beach. The cab driver dropped us off first, I can't remember the exact fare, but I think the cost was $20 for the four of us, and I gave a $5 tip. The driver told us to walk down to Orient Beach to get the cab back. I think she liked the tip, as shortly after the DCL excursion group left, one of the workers came in and told us our cab was waiting but to take our time.
When we were ready to leave, we asked her to take us to the shopping area, where we again took our time going to the various shops. At the end, we took the water taxi back to the ship.