The edition 30 has held its value so well because -
1) vw has a huge cult following who will pretty much only buy vw or always look to buy a VW
2) One of the best if not the best gti ever built is the mk5 IMO - No doubt someone will pipe up and says eh no it's not its the mk2 - well why didn't you save your self 5k and buy a mk 2 then ?
3) The edition 30 is the pick of the Mk and has a huge tuning potential with the best 4 pot vw has ever made couple this with limited numbers and you have a limited supply with a high demand which will push up the prices.
Also for 10-11k I really can't think of anything on a 57 plate that's better for similar money ? Can anyone else ?
Sure we can go back to 2004 and say a 70k m3 but having owned one I'd rather have the Eddy modded.
Look at other cars in a similar position mk2 focus rs - amazing car with brand loyal enthusiasts and holding its value unbelievably well I bought mine new kept it a year and the dealer bought it back off me for nearly as much as I bought it for.
A well specced nice example of an edition 30 will command a further premium to enthusiast -
Having had both mk5 GTis and ed 30s in the past I'd say you can easily have the same fun in a 2+ gti as you could in a 2+ eddy obviously not quite as fast but not worth the upgrade if you already have a gti in the first place however if you are going ko4 on a gti it makes financial sense to sell the gti and buy the eddy and I would always recommend a eddy over a gti to a first time buyer
In conclusion why are good ones going for 10-12k ? Simple because it's one one of the very best cars you can buy right now in its class and with a few quid spent in the right places it can become a completely awesome tool yet still retaining every bit of drivability you'd expect from a daily
The edition 30 one of the very best vws ever made !