Not all smart fares earn 50 credits, so I'd guess you are in for 9k ish
Cheaper option currently is AerSpace on operated services in Europe, a return gets you 100 credits for 300-450 euro (after 1 Oct fares are bit crazy though we expect this to reset) so about 4k which is getting into really good value
Is concierge worth it though?
No seating priority over any other status level
You do get the change fee waived
4 upgrades (only useful if you fly to US/CA) and book well ahead
Free WiFi if in economy on TATL
No status recognition outside EI
Platinum status is good enough really