Origin doesn't tell the whole story
Overstock can be an unused item, a product from an older collection or something that has been in storage for a long time. A returned item may only have an opened box, but it can also have faults or missing parts. «Returned item» is a label, not an assessment of technical condition.
Look at the test result for the exact unit on offer. For electronics, the battery and ports matter; for furniture, the fittings and dimensions; for appliances, a working test. A factory photo cannot replace a list of what is actually included.
Work out the real cost
Add the cost of missing accessories and any servicing. For an older model, check before buying that the filters, batteries or software support it needs are still available. A cheaper item can end up worse value if it needs a hard-to-find part.
If you are buying several units, find out whether each one was tested or only some. A photo of one working unit doesn't confirm the condition of the whole lot. Also look for signs of storage damage: moisture, corrosion, warping and the effects of long storage.
Judge each offer on its own
On the lot page, check the origin, condition grade, seller and collection terms. Don't assume a returned item automatically comes with a manufacturer's warranty, or that overstock is always unused. Decide on documented facts and a level of risk you are comfortable with.
