Keith, the GAIA are indeed listed on Amazon for $189, and B&M stores are selling them for $199. They were developed to be used as feet for loudspeakers, in place of the stock feet (if any) or spikes. But they are also appropriate for turntable, including your HW-19. The GAIA III can be used in place of the stock VPI rubber feet that came on the tables base, in place of the suspension springs inside the base of the table, or both.
You can read the review of the GAIA (and some other IsoAcoustics feet) in the June Stereophile by Art Dudley for any other clarification you need, or read about them on the IsoAcoustics website.