I'm still using one of the HP and a few of the HPx models on my bikes. When the mechanism to switch between 'x' and 'HP' failed on one of them I checked at the next swap meet for a replacement. Got one that was in perfect condition but too short for my bikes for $3, another that had a dent in the tube for $2, and one that was missing some of the valve connection parts for $5. Combined the last two to get a good working pump to put on my bike and am using the first one when I want to patch a few tubes at my desk. There were also a few HP models available at similar prices but I wasn't really interested in those.

Certainly no sign that they are inordinately valuable in this area.