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there are only a few places where its cost effective to implement"
This is repeated often, but is wholly false, each time.
Often it comes with a claim that an existing, elevated watershed is needed, which is false. A watershed is needed only for regular hydro generation. Most places suitable for that already have dams, many of which can be used for pumped hydro storage. Many are. But that is just a matter of convenience. The claim is often made hoping to confuse readers.
Some claim an existing elevated lake is needed, which is false. An earthen dike at a hilltop suffices. Such a dike may be needed only at one end of the reservoir.
Some insist an expensive concrete dam is needed to provide enough "head" to store much energy. They either have not heard of a penstock, or pretend. An earthen dike suffices. "Head" is the height of the hill, not the depth of water behind the dike.
Some insist a copious water supply is needed, which is false. Water may be stored at the bottom and pumped back up, with only evaporative losses. Such loss may be reduced by floating solar PV on the reservoir. Some places can use sea water.
Some insist a mountain is required, where in fact a hill suffices. The greater the altitude, the more energy each ton of water stores, but a few hundred meters height is plenty. In places with underground cavities, even the hill is optional. Using an underground cavity for the lower reservoir can radically increase the head available, vs. just a hill.
Few places are very far from any hill, or cannot afford evaporative loss from a reservoir. Such places will use other storage.