Remember to take the cost of ATPL theory course plus exams into account as well.
There is no " standard" conversion anymore under EASA. Under JAR there was in many countries a minimum of 15 hours for a conversion, now it is based on your skill level and decided by the Head of Training of the FTO you choose to do the conversion with. You need to have passed all the ATPL exams though before you can do the conversion.
As for where it is cheapest , that is definately in Poland. A bit of a newcomer for flighttraining but a full EASA member with some excellent operators. I would say compared to Spain that Poland is at least 30% cheaper (and the instructors/ controllers actually do speak English
) and easy to visit from Skandinavia.
I did a large part of my training there and I can only recommend it, especially now you simply do the training there, but any other EASA country will issue you the rating/license. I heard of guys doing the conversion in Poland fully on aircraft for less than €4000 for the full ME/IR + CPL when they already had the theory, so definately worth checking out.