I know a few people that found PoserPro very helpful and worth the upgrade cost. The main interest for them was the render queue , so they could continue working while rendering . It also allows multiple projects to be queued for overnight processing .     If you are really a professional any improvement in throughput is helpful.

Personally I think Poser is dead unless it gets picked up in the professional area. Daz Studio has made a big move in the hobby market and will do better if it gets a cloth simulation package . After all why pay $250 for Poser when studio is free, particularly for a beginner.

$500 does seem to be a big increase for what you get but that price tag for a commercial shop is petty cash.  One decent job pays for it all.