rotaries is absolutely correct; cones and spikes are not isolators, they are couplers---at least, in the very low frequencies needed for turntable isolation. The idea that cones and spikes provide wideband isolation seems to be a deeply-entrenched misconception amongst hi-fi fanatics, one that persists in spite of overwhelming proof to the contrary. Cones and spikes DO provide some isolation above around 10Hz, but below that frequency couple, not decouple, two physical bodies (such as a table and the shelf/platform it is sitting upon).
The Newport and MinusK isolation tables are state-of-the-art (providing deep isolation to at least 2Hz), but rather expensive (over $2000). A cheaper, and admittedly less effective, method of achieving isolation is with a combination of lateral and vertical decouplers---roller bearings for the former, air springs (or metal ones) for the latter. A mid-priced solution is the Townshend Audio Seismic products, available as single pods, platforms, and speaker stands. Audiogon member Folkfreak employs the Townshend Seismic products in his excellent system.