The Summilux 50mm Aspherical is my most favorite lens for its perfect rendering, its a super solid lens that at times suffers from flare but other than it, basically is near perfect.
A sharp lens even wide open f/1.4 and soft rendering on the out of focus areas. Look at these images and judge for yourself:
Sometimes you can find it at Amazon for about $3000 in used condition or open item, if you keep an eye you’ll eventually find a good price. The lowest I’ve seen it go is $2600. Here is the direct link to Amazon: https://amzn.to/2WLaIMq