I tried selling decorative plants for a few months but I didn't really sell much. What did sell was the mutated plants which I sold for 20k each. Now instead of selling the plants I make natural dyes out of them and sell them for 60k ( a little bit more of a profit ) and I can't seem to keep my vendors stocked. I've been thinking about increasing the price due to demand but I haven't, I'm comfortable with the price and my customers seem to be as well. My vendor sells what I get from gardening so orange petals, red leaves, green thorns, seeds of renewal plus some other random things like enchanted apples and enhanced bandages. I turn enough of a profit to keep the vendor up but nothing I will get rich from.
Edit: To answer your question, I typically sold my non-rare decorative plants for 500 each. You may have a hard time selling them at 10k a piece. Also depends on if you have any competition. Take a look at vendor search and see what other people are charging for comparable plants.