Nipputz literally means carding wool by hand (as opposed to machine) and would be done Lishma. Due to the manual process the prices would be significantly more expensive than the prices for non-Nipputz strings. Some prefer Nipputz as it’s an extra hiddur. Should there be a demand for Nipputz strings down the road, extra consideration will be made to order some sets of those in the future.
This is a video demonstrating how manual carding is done, but in addition Leshem Mitzvas Tzitzis is said while doing it: