While it's impossible to say (and I'm not even sure there's any good reason for wanting to know, outside of studies where it ought to be measured precisely) I can tell you that the last time I used an MTL setup I used 18 mg
juice, and that with an airyish DTL RDA I use 6mg, and subjectively feel as if I am getting at least as much nicotine from that, even given that I don't hold it as long.
So, _in my specific case_ it's likely that the ratio is greater than 3:1 (I would actually guess more like 4:1.) Unfortunately that's a very loose guess even in my case, and even if my guess were very accurate (it's not) it would differ for everyone based not just on what equipment they used, but on how they used it.
That said, if you're looking for very rough baseline numbers 3:1 to 6:1 is _probably_ in the ballpark, I think, for most people. That's a very large ballpark....