I sold out of Black Cherry and Sungold and came close to selling out of Gregori's Altai (once I told people what it was). If I wanted to get serious about this, I'd probably also grow Isis Candy and Sweet 100 seedlings just so people can get the whole gamut of cherries.
I could have sold more Arkansas Traveler and Cherokee Purple seedlings if I'd brought more. People know about those. I upsold a couple of people on JD's once I told them I have tasted CP and JD's side-by-side and liked JD's a lot.
It's funny how every tomato plant sale usually involves an entire conversation. I think I talked one guy out of using 30-30-30 fertilizer on his tomato plants this year.
"Did you get a huge bushy plant with no tomatoes?"
"Wow, how did you know??"