Broadwell is likely to come out this fall, with Skylake coming out Q4 next year (I know it hasn't been confirmed, but let's assume these dates). Broadwell may be a minor refresh, but has much higher resale value compared to its 250 days+ outdated 2013 model. How much should I expect to pay to upgrade my $2300 i7 8GB/516GB Broadwell rMBP for the equivilent 2015 Skylake version? I understand it varies, but a rough estimate (even from people who've upgraded their MBPs before) would be great. Gazelle is out of the question, they quoted a flawless one at 50% retail.