I also would like to post some positive reviews related to Unity asset store items and recommend it for all the users who try to avoid to spend their money on crappy stuff.
The BIG ENVIRONMENT PACK by Philipp Schmidt contains various Unity vegetation models (trees, bushes, etc.), buildings, particles, rocks, organized into multiple scenes and an to an inventory. To be honest, I decided to buy it because of the vegetation models.
I was lucky to get it in a 50% deal (daily deals, regularly discounted prices are one of the cool features of the Unity Asset Store).
The exported models from Unity could be used in Blender Game Engine, too (I made a quick test). Since I worked out a reversed pipeline from Unity to 3DS Max, it could be used even in Max.
You can find this asset in the Unity Asset Store here.