I think we do undervalue our cars at times,especially cars like GT4 s,but its still down to what people are prepared to pay for a particular car.These days people don't want to pay top dollar full stop,which is why I think some of the sellers have the piss taken out of them,though that's usually because they are taking the piss anyway.Those aside,most people will price their car for what they think its worth.take gen4 s,generally due to rust and age they go for pennies,problem is the knock on effect means a perfectly good one still struggles to fetch any decent money purely because of the ones that pop up that are projects or sheds.An older Celica is only worth what the buyer wants to pay.And in a lot of cases,worth more in bits if they've been modded,which is a shame.Crap for a seller,but look what you get for a few hundred quid to under 1500 .It's partly why our cars are so popular ,huge value for money,but unless you have a rarer model like a CS or that ilk,you ain't buying an investment.but that's what separates enthusiasts from owners.....