Just bought a 2015 13" rMBP BTO 2.9/16/512 and wish I bought the 15" base model as I am using a larger ThinkPad T450 in work and the screen now seems small. I cannot return it for a replacement to the reseller as its a custom order. How much will I lose to realistically sell it? £150, £200, £300 cheaper? Boxed with all packaging, as new condition, power supply not unwound and only used for a few hours.