The pricing structure on the main PostPath Server™ is based on a per-user-account model (quotes are provided upon request).
An ordinary user account that provides Outlook™ and other support includes web client access at no extra charge.
You can also buy user account licenses that are restricted to web client access only, for users who do not need Outlook™ access. These are priced at half to one third the price of a full-access account, depending on volume.