Wire leaders are necessary when battling fish with razor sharp teeth which can cut through the best of lines. Making your own wire leaders is simple and can save you lots of bucks $$$.
When fishing for species such as dorado, I use 135lbs coated wire from the American Fishing Wire Company. I crimp on a size #6 Berkley Cross-Lok Snap on one end of the wire and crimp on a size #4 SPRO Power Swivel on the other end. I normally make the leaders about 9 to 12 inches long.
For tigerfish and other species which don't grow as large, I might use 70 to 90lbs wire the the same above components.
Recently some companies have come out with knotable leader material such as TYGER. This wire is very flexible whereas you can tie all your basic knots and eliminate the crimps which are often the weakest portion of the leader.
So, try making your own leaders before your next fishing adventure and save some $$$$