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The hotsprings dealer will throw in the cover lifter already if you pay cash/check. My theory is that it can't hurt to ask and that most dealers are more likely to give freebies than drop the price further.
One of the reasons they include (if they cant sell it to them first) the sub panel is because you cant buy them any where that I know of, could be wrong, or can you buy such a thing at Lowes/Home depot?
Jim, I'm not sure about the US market but, here in Canada Home Depot sells both Siemens and Square D GFCI breaker panels for spas, prices range from $125 to $250 pending size.