I think you're thinking of it a bit backwards.

Why limit your price to LTV for the offline-only version? Think of it as a full blooded product, instead of trying to squeeze it into the SaaS thinking model you've got already.

Plenty of enterprise (and such) clients wouldn't balk at all at a $500 fee. Brainstorm your target market and price accordingly. In other comments, you're mentioning the support burden - I don't think you should sell the offline version if you're not ready to lift that burden, and thus should price it in a way where this is attractive to you.

Offline versions are usually used by more demanding customers in the current day and age - the web is where you go for the user-friendly version.