I think this may be cheaper than most people are thinking, somewhere under $3500. Keep in mind mirrorless bodies are cheaper to manufacture than DSLRs. So comparing this to the price of the 5D4 when it first came out is not quite an apples to apples comparison.
Could Canon still go ahead and release it at a comparable price to a 5D DSLR and have no one bat an eye? Sure. But I suspect they will be trying to pull as many people into the RF ecosystem as possible. It's much better to get people into this camera and sell them RF lenses and future bodies for decades to come than it is to try to profit that much on this camera specifically.
It ultimately depends how aggressive they want to try to be. But I don't think there's any way, with how much pressure they're facing to make the RF system a success, that it comes in over $3500, even with what it can do. The amazing video specs are the icing on the cake, not the thing that they will use to try to justify making it cost over $3500. And if they really want to send a shot across the bow of Sony, they will undercut the A7IV price. Canon has enough other revenue streams that they could probably price it below $3500 if they wanted to.
Let's also not forget that if the leaks are true, the R5's 45 megapixels is still lower than the Sony A7IV, so for a lot of people, especially those who don't care a lot about the 8K video, the R5 may look a little less intriguing than the Sony. So pricing it over the Sony would be foolish.
I say no higher than $3500, maybe even as low as $3300.