The bridging issue has been a big problem. I have never lived in a building that has the issue, so I don't know really what the energy cost is to the end user. I am sure there are plenty of studies on it. On a project I worked on a little while back, we used products from these guys
https://www.schoeck.com/en/isokorb and there is a lot of good literature on their site about the problems and how their products help remedy it. Seemed easy enough to install - just cost a decent amount and took a little bit to get. I at least appreciate that they're trying.