Value is very subjective. They're meerschaum (hydrous magnesium silicate), and probably date to the last 10-20 years of the 19th Century. This is a set of cheroot holders, a cheroot being the style of cigar which was later eclipsed in popularity by larger cigars. The round section fits into either head to hold a cheroot, and the blank spot is probably for an attachment to hold a smaller one such as a cigarello. So you'd select a head, insert the proper holder, insert the stem, and smoke.
The heads are, in my opinion, caricatures of the then-accepted image of what a "negro" looked like, with exaggerated nose and lips and big hoop earrings. This set are probably a woman (with the wilder hair) and man.