That's a math conclusion so lets show our work
Minimum wage is $16/hr in California + employee overheard so lets say $25/hr. With 3 people covering shifts at the drive thru, that's $219k per year.
Now for this system, lets look at off the shelf retail API prices to get a conservative guess. $0.006/min or $8.64 per 24 hours to listen & transcribe the customer, then add TTS + GPT-4o for $50 per million tokens in and out (thats way more than they need for a day). So that's $21k per year.
So back of the napkin math says it's 10x cheaper to implement this system. Unless you're referring to the corporate R&D budget.