Studloop grew out of our own LEGO parts store. We ran into the same things you do: keeping stock aligned by hand across BrickLink and BrickOwl, double sales, and no view of your real margin.
So we built it ourselves: sync between both platforms, order processing, invoices, and the figures we were looking for. What we use every day, you can use too.
You connect your own accounts and your data stays yours. When something changes on the BrickLink or BrickOwl end, we sort it out.