Keep convincing yourself and eventually you'll believe it to be true.
There's really no such thing as a no-tax sale, it's a scam! In case you or someone else hasn't figured it out, it's percentage reduction sale where the price is reduced by the percentage of the tax (the store still has to pay the sales tax on the item to the state.)
I don't know about Sam's, but Costco doesn't have sales. They do have coupons and they are realistic price reductions, but they're also funded by the manufacturers, not the retailer. Find it kind of odd that Sam's would have such a sale, it really doesn't fall into the Sol Price business model that Sam's is patterned after (as is Costco). As such, your description of the generator transaction and pricing would seem correct and would not be diviating from their already reduced pricing.