The prices of smartphones – of all electronics, really – are going up, so this might be a bad time to upgrade. However, this also means that old devices are retaining more value and Apple has recognized that as the company just updated the trade-in valuations on its US site.Many older iPhones are now worth a bit more than they were just a few days ago (we got the old numbers from the Wayback Machine). Some are just $10 more, but there are plenty of models that went up by $25, some even $35. iPhones Model New trade-in value Old trade-in value ...