"I had always thought that the cost of the high end programs was because of the tools, interfaces and in some cases the ability to multi-proc." It is ... mostly it's all about development and R&D time. I would SERIOUSLy doubt that Discreet (3ds max) is payign more than $100 per license for the Mental Ray engine - probably much, much less. BTW - renderers like Terragen are usually extremely special case for landscapes... and as such don't really "fit in" here at all.