Why aren't there more Blu Ray/DVD transports?

I suppose it's because there is not a lot of marketing data to support that a x-port only will sell enough units to be profitable.IMHO.

because a cheapo Blue Ray DVD sounds the same

You don't have to pay twice. There are many low priced BD players that offer HDMI to go to a pre/pro (use the DACs there), while only offering analog stereo outputs (yes, they use DACs for that), and usually a coax or toslink output (for external DACs or pre/pros, but no HD codecs).

You don't have to purchase a BD player that has multichannel analog outputs (which use multiple DACs).

I'm wondering why the OPPO b83 is twice as expensive as everything else. I have a standard def oppo I like a lot but $500 for blu-ray is a bit pricey compared to the competition. I suspect the price is high because OPPO got a good name in the reviews and because of all the supported formats. I don't believe I'll be paying $500 for it though.

To rephrase the question you're asking:

"How much less would (insert your brand here) charge for their (model XYZ) BR player if they pulled the DACs out and called it the model XYZ BR transport?"

So, a bit of speculation:

AFAIK, the guts (including transport section) of all current BR players are all manufacured by large electronics companies. For these firms, costs are largely driven by volume - and whatever component costs could be saved by pulling the DACs would likely be offset by the costs of running a smaller volume product variation.

Bottom line: pulling the DACs out of most BR players could actually increase the final retail cost of the product.

If the market will support it (a resonably big if), you can expect smaller firms (variations on Oppo) to start marketing transport only BRs, because their economics differ, and omitting components actually will lower their product cost.

Just my speculation.

Marty