First off, I'd just like to point out that we are in danger of conflating Kent's issues with the Preserve with a more general question of the impacts of "preservation". The 100000acres referred to in the plan is obviously not going to end up being an extension of the Preserve and to imply so is absurd.

I would be interested to know exactly how much $$ is actually 'lost' because the Preserve sits on 7000acres of unimproved, tax exempt land. However, to focus solely on the loss of local tax revenue as though this is some form of subsidy to visitors seems to miss the point entirely, since it implies that this is the end (loss)of the economic value of that land to the community. Well, a little lazy Google shows that tourism contributes >$400M to the overall economy in Ulster county, or roughly 8-10% of the total economic activity for the area.

tourism $ for Ulster county

2005 $427,190,073
2006 $471,731,320
2007 $489,814,060
2008 $470,180,331
2009 $420,160,000

Look at the numbers in the link, and especially the higher numbers for Ulster compared to its neighbors. Most probably people enjoying the parks, preserves etc i.e. the preserved state of the land. This equates to over $2K for every Ulster county resident. That's a lot of dirtbag dollars that filter into every pocket and into the community coffers as a result of local taxes.
The Preserve could pay more, but as Rickster points out, the Preserve would be idiotic not to preserve its 501c2 status, I'm also not going to deny that some people (Kent) etc are negatively impacted by the existence of the Preserve and their immediate proximity to it but I don't think based on this that, on average, local communities are effectively subsidizing our recreation i.e. are, on average, worse off as a direct result of preservation under tax-exempt status as is implied. I don't have numbers that break this issue down further but it seems obvious that the very existence of those preserved areas directly generates economic activity that would more than offset any lost revenue.