It's a feature license that has to run on a Cisco router. Most companies don't use a router for their VPNs but instead use a Cisco ASA firewall.
That said, the list price on that particular product is $750 but is is normally discounted 30-50% so has a fair market value of less than $500 and is of little to no use without a router to put it on. It may not even be legally transferable from the original purchaser (who likely bought it with a router they had in their company).
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...