I don't agree with my husband's keto diet!

So my husband has been struggling with his weight and decided to give keto a go. I always thought keto meant cutting out the carbs and replace that portion of the meal with vegetables, but he is only eating meat pretty much. He'll eat some cheese too sometimes. I bought four pounds of meat, thinking it will surely last at least two meals, but he ate it all in one sitting! It's an ridiculous amount of meat! I've tried to tell him it's not financially sustainable to only eat meat, and in that amount. Also I'm questioning how this diet will make him lose anything because I'm thinking he's eating way too many calories. It seems he's over compensating for those carbs he doesn't eat. I'm no expert, but I'm sure you need to eat less calories if you want to lose weight. It's causing us to argue, because now he spends hundreds of dollar each month on just his meat. Of course I want him to be healthy and support his journey, but I think this way of eating is making him even more unhealthy. Am I right or am I wrong? I'm happy to be educated. This doesn't make any sense to me.