Hybrids have been the easiest way for me to get bells on Animal Crossing from other players. I mean, most of the time, people who sell hybrids need the money (I know I do for my dream town development)
I've been lucky with quite a few of my hybrids, I've even managed to get some Black Cosmos and Tulips. And I wasn't even trying for those xD I had a lot of trouble with Blue Roses though, so I traded some other hybrids for 4 of them. I don't think I'd ever buy any though. It does seem a bit silly.
One of my challenges was to grow all of the hybrid myself. That challenge was completed awhile ago.
The blue rose grow so fast and I give two or three away for free to my group.
A lot of people are buying flower in certain colours. Just having pink only flowers would take along time to grow on your own.
So I can see them asking to buy.