Well for me, the purchases were between 100-300l each over a period of time, I really should have spotted it earlier but was distracted from SL due to RL, I only noticed it as a problem when I realized I didn't have enough L to continue paying rent on my store land.
Thankfully, after pushing to keep the ticket open, Dakota Linden put the issue to her supervisors who agreed to re-credit me the lost profits, which I am very greatful for.
It goes to show that the current magic box system is flawed, and I hope that these issues can be avoided completely when the new magix box-less delivery system is launched.