Depends. Are we taking refurbished, or returned sales?
Refurbished is going to have to be hella cheap to consider it for a highly redundant storage of unimportant things maybe raid 10 backup storage it something.
Returned sales are mostly still as good a new and returned for various unrelated reasons. As long as I get full warranty and right to return as if it was brand new, i don't mind.
I run used disks with tens of thousands of power on hours. Yes the risk of each disk dying is higher but only marginally and the cost is dramatically lower. To avoid data loss when they die, I have functioning backups. This system is working really well for me.
Having worked at Amazon processing customer returns, you do not want to buy drives that have been processed through Amazon customer returns. We took them in whatever package the customer sent them in (I've seen gallon size ziploc freezer bags), which are just tossed into a big UPS box with who knows what else, then jittered around on conveyor bars, and then it goes into a thin plastic bag (not anti-static), thrown into (this is not an exaggeration, a lot of employees toss the items in like Kobe, it gets boring after your 900th item this week) big plastic staticky tote bins clunking around underneath who knows what else, jittered and clunked on the conveyors again, and then eventually sent to the warehouse deals desk. All protected by nothing more than a thin plastic bag.
I'd actually trust the refurb more than returned customer purchases.