They certainly sell well on console. Not sure what platform you're on.
I can sell Kutas for 5k+ on XB NA.
For plants, here are some examples. Again, these are XB NA.
Cornflower - 400g each
Columbine - 300g each
Blessed Thistle - 250-300g each
Lady's Smock - 250-300g each
Dragonthorn - 180-200g each
Now, this is at a trader in Mournhold. Also, price fluctuates and for a while, I couldn't sell Dragonthorn for much more than 120-150g each. It also depends on how many players are trying to sell alchemy mats. Around Summerset, it seemed like everyone in my guild was trying to sell them, so prices went down. Lately, though, I'll check prices in my guild only to find very little plants actually for sale.
If you're on PC, you could use the MM add-on or check TTC.
All mats (except most enchanting and food ingredients) sell well.
And are pretty easy to gather (resource bonus is a must have), I'd average a resource node to be at least worth 75c, this adds up fast.