It was super low effort. Buy wholesale on Alibaba, tell the seller to send goods to packing, and silkscreen shop, and send by regular post to my apartment. Very often, fancy packaging was costing more than sunglasses themselves.
Even when I was buying crate loads of goods, I only got a customs bill only like 2 times out of 10 in 3 years. Customs bill was pretty much nothing, and they never contested the valuation, but the extra paperwork was very unpleasant at the time when I had to study.
Then you sell $1-$2-$3 sunglasses at $100+ prices. Just make decent websites for all made up brands you have, have good marketing fluff, and make sure to call them with some Italian/French sounding name.
You make at around 10-15 sells per month, but what else you want with that level of effort? Second to that, I was very unsure of my tax/legal status at large if that business were to become too big. Being kicked out of the country, with all my money in that degree wouldn't be fun.