$200 SX's can't hold a candle to a T-40, so that's right out.
Sire is a better comparison, but there's some holes in that one.
-Component prices:
Sire basses use alot of standard off-the-shelf components. That brings the cost way down. A T-40 has special (and more expensive to produce) bridge, plate, pickups, knobs, etc...
-Demand:
Sire is making a Jazz Bass, one of the most common and well-liked basses in the world. There's a huge demand for well-produced and affordable Jazz bass. Is there really a huge demand for a mostly unknown, very heavy bass with esoteric controls and a p-bass width neck? I don't think so.
-Asking Price
Maybe you could make it at $700, but then you're pricing a new import for $100 higher than the vintage original and that will shrink the potential buyer pool even more.
As I said earlier you could do an import "T-similar" bass for $500 that would actually sell well by, shrinking the body and using off-the-shelf parts and pups, but then it's not really at T-40 anymore.
The appeal of the T-40 is 4-fold as it's a..
...good sounding...
...Vintage American...
...bargain priced...
...absolutely unique...
instrument.
It's why we put up with the massive weight. Take any one or two those away and you massively decrease the already small audience that this bass has. I think an import T-styled bass at the $500 could actually be a seller, but it couldn't be original specs if it were to be successful today.