According to Sindy Starlet's insta story, she got hers (filled to 1650cc upon operation) for EUR 10,000.
Strangely enough she later put in her story that Plovier only had 3 pairs of expanders left (can't remember exact reasons, something with regulation/production), and that these would cost EUR 18,000. I am not sure about this is correct, this is along the lines of what she wrote though.
Probably the best source is to contact Sindy Starlet yourself, I think she would be happy to hear from someone with the same interest as herself.