I would go for it. The machines I see in our conditions with 1000 hours that have the high wear package are worn down pretty good. We won't sell a machine without the package since it causes problems at resale.
We have the high wear package on a 9760 with about 1000 sep hours now and looks like wear stuff will go a long time yet. I have never owned an STS before so can't comment or compare on a machine with out it but based on the wear where the hard surface stops I am going to say that we would have replaced a bunch of parts by now without it. You will have to be the judge if the dealer will pay you enough more for a machine that he might be able to resell without much repair compared to one that he has to rebuild. If you are going to keep the combine for more hours I sure think it is worth the extra cost.
i don't know what field conditions you run, but i know that if you have any issues with rocks, it costs about twice as much to replace the high wear elements and tines, other than that, the machines i see with that package can run for many hours
With the packages deere offers, it only costs about $3400 to add both the separator and unload high wear. I don't know why anyone would not get it with the increased life you will see plus added trade value.