The Denmark to Sweden bridges are less expensive if you pay a yearly fee, it's usually worth it even if you only cross two times.

However it's not straight forward to figure out the optimal way to get from say Hamburg to Gothenburg. You can take the short ferry from Fehmarn to Rodby, and then take the bridges. Or you can drive all the way via Odense and the bridges. Or you can drive to northern Denmark and take the ferry from Fredrickshavn over. Or you can go to Kiel and take the overnight ferry straight to Gothenburg, which is expensive but you can sleep all the way. Then there is the Travemünde-Trelleborg ferry which could also be an option...