finisher,
Eric correctly interpreted my suggestion; simply drop your seven subassembly files into a new top level assembly file. This is only seven file insertions rather than 87. Since you are only interested in the BOM information then this is simply drag and drop with no mates required. This is very simple.
And yes, using the indented BOM provides a lot of information that is then easily manipulated in Excel.
As I reread your original post you already have a lot of this work done, i.e., it sounds like you already have a top level assembly file and it even has a drawing so you should just need to generate the BOM, either in the assembly file or the drawing, and then export it to Excel. It sounds like the only real issue is generating the top level BOM the way you want it.
If you do not have any suppressed components in your subassemblies you can Dissolve them into the top level assembly. This might benefit you by combining your BOM components similar to how you have the BOMs structured for the individual subassemblies. I have never had to use Dissolve since I've had enough options to control the appearance of the BOM with the available choices. (Besides, the Dissolve apparently only works if there are no suppressed parts and I usually have several configurations controlling suppression states.)
You should be close to achieving what you want, just work from the top level assembly you already have.
- - -Updraft