I just left Costco after five and a half years as a corporate IT guy. It's not all it's cracked up to be. There was a time, and this was true for Home Depot and Walmart and so many other retail companies that if you got in on the ground floor, it was great. My father worked at Home Depot 25 years ago and made some bank on stock options they would give everyone. Not anymore. I worked with a guy that had been there 30 years, mostly in corporate offices and had plowed every cent he could into Costco stock in his 401k (which they allow employees to invest in). He's a millionaire. That can't happen again. The days of high growth are over. It will only be incremental gains from here. Plus the wages, while they seem good on the surface, have not kept up with inflation. Retail workers earn way less than their compatriots that started 20+ years ago. The hours have been slashed. Most are part time now and not full time to save costs on benefits. Then it's a retail job and it takes YEARS to get to a position where you are not running your ass off all day long.

Your story is simply one of a person that was an agressive saver and happened to pick a winning stock as a large balance of her portfolio. In simpler terms, she got lucky. It has almost nothing to do with Costco.