Storage
Space could be a serious cost consideration here in Hong Kong as space is expensive in a very densely populated city. Next to that, as sales will quite likely go through small channels (micro retail, small chains) selling only a few at a time, storage might be required for several months before we have sold all products (foreseen in cost profit calculation for two months). Fortunately there are some good options. Costs in HKD/month (roughly multiply by 1.25 for USD).
Shipping
Not investigated in calculations. However as quantity is low and it will be transported from China (south of China, close to Hong Kong) to Hong Kong I predict the costs for transport and customs will be relatively low.
Sales Channels
Sales will quite likely happen via micro-retail channels, not directly via bigger chains as they normally have all kind of requirements before you can work with them. That being said, it was still interesting to see which bigger retail stores would be a good fit for this product.
Conclusion
I decided not to continue with this project, simply because the costs hardly equal the profits for these small quantities and there was no funding for ordering higher quantities at the time (2018). I did not consider other routes, perhaps a Kickstarter or IndieGoGo could have made a difference but this product is not that special or innovative, so doubtful it would be successful.