It was a joint design and I doubt any single element such as audio will make it a flop or otherwise.
But anyway, regarding the subject of the thread, yes Oculus could offer trade-ins but there would be a... erm… trade-off and that would be price. There has to be a profit margin of some sort, so trade-ins would mean higher cost of the replacement, it happens with any trade-in offer, the costs are usually just hidden to the consumer. There's no free lunch.
Edit: on the other hand, there's ebay!
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