There were no production 50mm f:1.2 Noctilux R lenses, only a few 52mm prototypes. I've seen a posting about a 52mm f:1.2 Noctilux R, but it was never in the catalog or full production, and it's very unlikely that it would be priced at $250 unless someone made a huge mistake. There was a Summilux-R f:1.4. No production Noctilux-R lenses were made. The one prototype 52mm f:1.2 Noctilux-R lens that I found online went for 30,000 euros.
The M mount rangefinder 50mm f:1.0 Noctilux may be what he has, but it shouldn't be at $250 unless it's in pretty poor shape.
You may need to check on the lens more closely, or perhaps the decimal point in the price.
Lee