Maybe it's different in Europe. I just looked up three shelters in my area and ONE had a yorkie type mix. No information about his age or health. Not many on the small side in general. Maybe here in the US these mixes are more desirable than Europe.
Just thought of this, While I'm here, I want to thank those people who are so kind and generous (ladyjane comes to mind) to go out of there way to foster and help the sick and old and/unwanted. I wish I was that good of a person.
I also did say that I would not pay the same for a mix as for a purebred. I have no idea what the dollar to euro equivalent is, nor what a purebred costs in europe. I do know a pure yorkie can be $1000 American, so the poster who got a pair for $450 American got a steal! If that is the going rate then the OP should be paying about half for the mix, or less since it is three breeds.
Very interesting article on a recent study concerning genetics and mixed vs pure. While mixed are not immune from genetic problems, the list near the bottom list specific conditions that seem breed (pure) related. At the very bottom, the yorkie is first for portosystemic shunt. Interesting reading. I would assume a mix of two breeds on the list for the same problem would be still likely to get that problem.
Mixed Breed Dogs Are Not Protected From Breed Disease Heritage | MyDogDNA