I just struggled with this. Last year, I went on my h's insurance plan (better coverage) and paid the $50/paycheck working spouse fee. This year, I studied the numbers more closely. By going back on my own insurance, I would save $922 / year. As long as I don't get too severely sick.
+$50 x 26 = $1300 (save on working spouse contribution fee)
-$33.75 x 26 = -$877.50 (cost per pay period to stay on my insurance)
+$500 HSA contribution by my company
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$922.50
I would go on my husband's insurance if my own company paid something close to $1300 for declining medical coverage but they don't. So, they will pay out over $4,500 for my medical cost plus $500 into my HSA.