The ultimate 50mm is the Summilux Asph 50f1,4 and I suspect that Euro 1000 could be a downpayment! As for a more realistic approach - I would look at the Zeiss ZM 50mm f1.5 C Sonnar. It is considerably less than the Summilux and it is more than competitive with it. The Asph is sharper at close focus, but when you get into the mid-range - they are equal, If you do portraits at f2-2.8, your subjects will be pleased with the Sonnar shots and most likely throw heavy objects at you after having seen the Summilux shots (very few of us like scalpel cut renditions of our face).
A Euro 1000 could also buy you a nice 90mm Elmarit-M f2.8 or a Pre-Asph Summicron f2. Or you could simply extend your lens range, get a Voigtlander 90f3.5 Apo-Lanthar and a 25f4 Color Skopar P mount (couples to the rangefinder of your T) or even a 21/4 Color Skopar P or LTM mount.
This latter combination would also leave you some money for film!
The amazing thing is the variety of lenses that we are now available to get for range finders. A decade ago, it was a rather limited range of new and expensive lenses from Leica or a large volume of used, older Leica lenses.
Today we can look at lenses from 12mm through 90mm from "other" manufacturers and speeds from f1.2 to 3,5. All at prices that are considerably less than Leica's offerings.
The quality of these "other" lenses is extremely high. Som are equal to Leica, some even better.
My feeling is that at the moment Leica has two lenses on the market that warrants their price and reputation, the 50/1,4 Aspherical and the 75mm f2.0 Apo. The rest can be substituted with Zeiss/CV offerings as new and if you add in some of the used stuff, Konica's RF series of lenses - and this can be done without loss of quality, either imagewise or constructionwise.
