I guess I must be the ultimate cheapskate. Filters in the 77mm screw in size are expensive so I did something different. Most of my lenses, MF and large format, have 77mm filter threads so I purchased a Cokin filter holder with the 77mm adapter.
Then I bought perspex off-cuts from the local plastic fabricators in red, orange, yellow, green, yellow-green, and blue. The whole lot cost $20! With a hacksaw I cut 84mm squares that fit the Cokin holder. Now I have about 40 filters at around 50 cents each.
To use a new filter I just peel off the protective paper and go. Perspex is virtually optically flat and does not degrade image sharpness; I checked. Unfortunately perspex is softer than glass but if a filter gets scratched I just throw it and reach for a new one.