I've had a number of cloud developers ask about using SpeedTree Models purchased from the Speedtree.com store. You can absolutely purchase assets directly from Speedtree, and if you don't have experienced artists on your team then it can be an easy way to get great looking assets quickly.
All you have to do is run trees you've purchased from their store through the compiler, just like in our speedtree tutorial video. I've attached a screenshot of two random trees from their store shown in engine: