Second Life, L$ 250
Avalaible at SL Marketplace:

We have our first models ready to upload. What to do next? That's the main goal of this book. We study the mesh uploader window, but we don't stop there: you will find a broad explanation of what exactly the Land Impact is and how it is calculated, what happens when we link objects, how we can optimize it even if we add sculpts to the mix, what LOD means, and how we can do our best to control/minimize the download and physics weights with the tools that SL puts at our disposal, so we can always find the best balance "Visual quality of our model/Land Impact".