I think Theo Wanne's mouthpieces are characterised by long facings and large chambers, often combined with high baffles (the Brahma and Datta are medium chambered). This follows on from the customised Links that he used to sell through his old website. The combination of large chamber and high baffle found in the Kali and Durga isn't too common -most high baffled mouthpieces I can think of are medium chambered. Whether this makes a great difference will depend on the player and what they're used to - some people can get a big sound out of a Dukoff - I can't..
Not everyone will get on with the long, Lawton-like, facing on Wanne's pieces, there may be a tendency for reed squeaks, depending on the make and cut of reed you use and your embouchure.
Choice of mouthpiece varies so much from one person to another - Milandro prefers his Brancher, I didn't get on with mine and sold it..
As for the price... well.... I've just looked at metal tenor mouthpieces on Sax.co.uk's website and there's not much that's cheap anymore - £415 for a metal Selmer Jazz - fill in your own expletives...
I think one of the reasons for Wanne's high prices may be that he seems to own a lot of expensive equipment - CNC milling machines and electro plating equipment etc - so we can assume that he's got a few hundred grand in bank loans to pay off as well as the rent on his premises. I think if I had to pay off a large bank loan every month, I'd be charging top dollar as well
There are other, cheaper options - Lawton, Morgan Fry, Pillinger etc or you could pick up something cheap on Ebay and send it off for a reface.
My only experience of a Wanne mouthpiece is of a second hand and well used alto Kali 8, which is quite a decent mouthpiece, but I'd prefer a bigger tip opening. It'd be good for a fat raunchy rock'n'roll sound, but not exactly subtle. I still prefer my Lawton.
Theo Wanne's saxes are made in Taiwan, although some of the more specialised parts are made in the USA and sent out to Taiwan. The finished horns are then shipped back to the States and set up and checked over by Music Medic.
I've not tried one of his saxes, so can't comment on playability etc. I'm primarily an alto player and he doesn't make an alto and I don't get on with Taiwanese ergonomics.
Is Wanne's stuff overpriced - yes, but so's Selmer and a few other manufacturers.
Are there some over inflated claims being made on his website - it certainly looks like it, but he'd not be the only one, Yanagisawa claim their thumb rest improves resonance, but I don't see much righteous indignation about them