OP is right regarding the principle.
1. Inconsistency – if everyone gets 2nd hand gift then that’s that but if not everyone should get a new one. Cheap or expensive.
2. Respect – that’s the mum and she should be precious. You don’t give left over food for your mum to eat so why give her the discarded stuff or item you don’t want? Perhaps, the son should give a new gift in addition to the old iPad. Yes, not to waste but that is not the way.
3. Honour – the son does not know how to honour the mum. Just like parents giving the children the best in life so children should do so in return. The children should honour the parents accordingly. Yes, some family is dysfunctional but that is not the question here.
4. Character – Sometime taking care of number one self should actually be number two. The son does not know the order hence put self first above all. A son should not put self above parents unless parents are wrong but then the son should explain himself first to avoid misunderstanding.
5. Shame – It is a shame that a son does not know how the parents feel (mother or father) as we can see OP’s feeling is hurt because of the son’s action. A son should not do that to hurt the parents intentionally or unintentionally. The latter is easier to remedy.
Tell the boy to buy the mum another gift (new depending on his budget) and not being a tight arse.
Also a person’s action tells a lot about a person character.
🙂