You might consider Silo. I haven't used it myself, but if I were in the market for a modelling package right now, it's probably the one I'd get. It's very cheap (about $100) and it's a polygon modeller (as opposed to a nurbs modeller like rhino or a metaball modeller like zbrush). The reason it's so cheap is that it only does modelling - no rendering, no materials, no animation etc.

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