Part of the reason why the Cornell market lags behind is due to a lack of exposure. There hasn't been a major Cornell show at a museum since his MoMA retrospective in 1980-81. Also, the work appears infrequently at auctions, art fairs and in galleries that specialize in the secondary market. Other factors that hold the boxes back are their small scale, sophistication and the fact that they're hard to display. This last factor cannot be easily discounted.
Collectors are generally more comfortable with paintings.
It's simply easier to hang works on the wall than find the space for three-dimensional objects. It's for the above reason that Cornell's framed collages just might have strong investment potential. Back in the early 1930s, when Cornell began making his first collages, most of the works were assembled from cutouts of old book engravings. Despite their lack of originality, the legendary dealer Julian Levy showed a few of them at his gallery. Eventually, Cornell's confidence grew as he began creating his series of boxes.