I wasn't particularly inclined to get into the discussion regarding the list of potential applications of the No. 5, but it seems the thread has sprouted a 2nd life based on a portion of a statement.
The potential applications are what makes the #5 a desirable plane to have. Fortunately for those of us who want them, they are possibly the most popular size plane available only rivaled by the #4. This helps to keep the old ones down in price a bit.

jtk