Title should read: 28 year old used to make millions buying from Walmart, selling on Amazon; because he certainly will have to live with competition and reduced margins from now on.
The company has been around for nearly 20 years (I've been with them off and on for seven of those years), and was one of the earliest online closeouts retailers back in the 90s. This is nothing new.
If you honestly think this is sustainable, you are mistaken.
You are lucky to have done well all these years, but as more people get smarter, bye bye margins.( Same thing in every business.)
More and more people will get into this space.
Sure, you may be able to survive because you geta volume discount on shipping, but that's all dependent on you sourcing the product that these new people will be doing because all it takes is a smartphone and dream....
It's been sustainable for the nearly 20 years the owners have been doing it, and the rise of Amazon and eBay has caused an explosion of growth over the majority of that time.
As for myself, my role there is multifaceted (mainly IT and website management, and helping out everywhere else as needed). I'm paid better than I was in government work, and I'm enjoying it a lot more.
And capital for up-front costs, and a willingness to take the risk to buy stock you might not sell, and space to store the stock before it ships, and people to do fulfilment, and knowledge of how to sell through Amazon (or any other site)...
If it was that easy then everyone would be doing it already. You can build a sustainable, profitable business doing reselling (thousands of people do) but it's hard, and risky, and that puts most people off.