I do not know whether you have to actually spend all 344 monocoins in order to get the items that way, or if you could obtain them from the MonoMono Yachine and still have it count that way. Either way, the vending machine within the Rocketpunch Market is what this is referring to, and if you were to buy the items normally, it would cost you (as mentioned before) 344 monokuma coins. But this isn't the only way you can obtain these items. It's just far more likely to get them this way than spending the coins in the Yachine for a chance.