Ohms law and LED driver efficiency? How can this possible be true?
He's trying to sell you something that consumes > 30 W as a "30 W driver", whereas it actually can only supply less than 30 W. The ratio between power that goes in and goes out is called the efficiency. The difference in power in and out is simply converted to heat.

You can upgrade your LED driver to a 2500W LED driver simply by putting it in parallel with a water heater of roughly 2470W, or any other resistor, for that matter. You can simply waste more energy.

So, that's what we call a scam and that's why we only buy from reputable sources in jurisdictions where one can ultimately sue someone.

As a personal note: Don't argue with someone who'll be getting your money. Simply make "fulfill this or don't get the deal" statements. Make the requirements verifiable, as in "The driver has to deliver \$x\$ A at \$y\$ V with a ripple of less than \$\delta\$ V and without getting hotter than \$T\$ °C in continuous operation. These are my requirements, and I can only pay for equipment that fulfills these."