[mothered]

It is 62 grams for the SSD alone (each), the whole package comes at 91 grams (each). This is 68% difference in weight and I would assume this will be noticed at some point.

You should've ordered each SSD on separate consignments.

Simply SE just the one- the likelihood of only one missing, will not raise suspicion.

Say I return the packages empty and the weight does not bother them, Currys/Samsung proceed to sell those to another buyer down the line.
Do they have the ability to crosscheck that I have returned these exact boxes and then come and look for their money?

Who's to say that the buyer (who purchased your return), didn't steal the Items?

That Is, did what you did by SEing the company?

I can also replace the SSDs with cheaper models and box them so there will be no weight difference, and upon them being sold to the next buyer they will be more likely to assume it to be a manufacturer error (if I do a good job at resealing the boxes).

This obviously Is the "sealed box method", that has a very high chance of success- provided there's no signs of tampering whatsoever.