I think you should study more about commercial aircraft's.
Secret missions. I worked as a network manager at British Airways. I know how much payload an A320 can carry and how to calculate it. The information is publicly available for you to do the same.
Payload is calculated by subtracting operating empty weight from max zero fuel weight. I've done the sums for you in my initial reply. You are the one who claimed the 737-800 carried 20% more payload. Payload in airline definition is weight. The 737-800 in the real world can carry at most 700-800kg more than the A320. That is not a 20% payload difference. Also, it's quite clear YOU are the one who does not know what he is talking about. Let's see here:
Because 737-800 is almost 10% more longer in Length, Carry 4% less Fuel, 7% More Seating space, 18% More Baggage space, 25% more Payload.
Airbus A320NEO (New Engine Option) Price $107 million
Boieng 737-800 Next Gen Price $ 95 million
Point 1 Length - Aircraft length doesn't matter to airlines. Pax capacity does. Real world you get 1 or 2 more rows of seats into 737-800.
Point 2 - The 737-800 doesn't carry less fuel than the A320. It actually carries quite a lot more. The A320 carries 18.7t at max fuel and the 737-800 a little over 20.5t.
Point 3 - seating space I've covered in point 1 but yet the slightly higher pax capacity of the 737-800 is a plus.
Point 4 baggage - A320 baggage volume 37.3m3, 737-800 volume 43.6m3. Both baggage volume capacities are adequate for 180+ passengers.
Point 5 - A320 payload 20t, 737-800 20.7t. 700kg more payload which is not 25%
Point 6 - Airlines don't pay catalogue prices for aircraft. Also, you can't compare a320neo with 737-800. Best comparison would be with 737-8 (max version).
Real world airliner price A320 44-47m USD, 737-800 47-49m USD
Next time you come to debate an aviation topic, make sure you have a clue of what you're talking about.