It's hard to say for sure, especially since the pressure of internet-direct marketing has made it harder for dealers to stick to MSRP's as consistently as they used to. Some of that 50% mark-up would have to be retained to cover the staff required for customer support and sales, services that (at least on theory) dealers would provide the bulk of for a manufacturer using a dealer network.

One possible indicator would be the Model 950, which was the basis for several dealer-channel clones. The Model 950's original price was $900, and the two clones that were most like it (different face plates and some inspecified parts selection changes) were the Atlantic Technology P-2000 at $1700 and Sherbourn PT-7000 at $1500. Another indicator would be the Model 990, which takes the Sherwood P-965 (MSRP of $1500 or $1600 I believe) and adds balanced outputs, a more robust bass management scheme, and DVI switching for $1100. Those would suggest that you might end up adding around 40% to the price to get a probable dealer network MSRP...