6ave (98.7%) has the Canon EOS 5DS R body for $2923 (Reg $3599) via ebay. This is the lowest price we've seen for the Canon EOS 5DS R.
*Caution: Earlier in the year 6ave had an issue with an EOS 5D Mark III sale that they oversold and then couldn't ship, and this affected their feedback as they had to cancel orders and issue refunds. The volume of this sale won't come anywhere near a big EOS 5D Mark III sale, so I think you should feel confident that this sale will go well. If you're not comfortable with grey market, Canon USA currently has refurbished Canon EOS 5DS R bodies for $3119.
*Note These are likely grey market items and may not qualify for a Canon USA warranty. Please check with the seller to see if they offer additional warranty.