I don't get it and it's bothering me

In September, the store is having a 10th-anniversary event. If you spend 99 yen on food, you can get a small lucky bag for 39 yen. The grand prizes are an i17pro, round-trip tickets to Japan, and a 3000 yen gift certificate. ---Below is a conversation with my colleague--- Me: OO, I noticed you haven't told any customers about this event. OO: I was too busy and didn't have time to mention it. Me: You can't be busier than me on my days off. (When she's off, I cover the counter.) This is a customer's right. What if someone finds out the grand prize was won at our store and they come to complain? Plus, I want the bonus money (there's a bonus for the top-ranked store nationwide). OO: We don't even know how much the bonus is, and it's impossible for us to be first. Me: What happens if they don't sell out? OO: We'll each take 10, and the boss will take 20. If we actually win a phone, we can sell it and split the money, which will be more than the bonus. Me: I don't want to do that. How is that different from when PxMart made employees buy unsold bread before? OO: The lucky bag is only 39 yen. Ten of them is 390 yen, which isn't expensive. We can just buy them ourselves. Another colleague: If she wins the phone, she won't sell it. If I won, I wouldn't sell it. Me: So, are you going to buy the lucky bags? (He shook his head.) ---The topic was dropped as customers arrived--- Is this a matter of money? 😡