Economical has no place in a titanium thread. Realistically, there are plenty of stainless steel alloys that don't make good blade steels but resist rusting well enough to require no more care than titanium. I'd be willing to make a small wager that such an alloy is currently in use in the Endura. Titanium would save you a few grams of weight, but the amount of weight savings would probably not be noticeable, and this is coming from a man who carries a CF military because the G-10 versions are heavier. I am not, however, one of those people who think "titanium" is justification enough in and of itself for any added expense. I'm quite sure the O.P. can get custom titanium liners made for his Endura. It shouldn't cost more than three or four times as much as the MSRP of the knife, and it would give him the bragging rights he no doubt wants. Asking Spyderco to shoulder the expense of producing them when even the regular repair kit seems to have been dropped from the lineup seems...well, selfish is one of the words that springs to my mind.