垃圾 is usually not considered a good (好物品) but a BAD (壞物品) because people generally prefer less to more of it.
If to some people, some 垃圾 is really preferred, for example, in the case of recycling paper, then 垃圾 can be a GOOD.
If our want for 垃圾 is satisfied given 垃圾 is a good, then 垃圾 is free good (免費物品 ). If our want for 垃圾 is not fuly satisfied and we are willing to pay a price / cost for obtaining more of it, 垃圾 becomes 經濟物品 (economic good).