Bread is vegan and lentils, tofu and beans are much much cheaper than meat where I live. I can see why it'd be harder if this wasn't the case where you are but I think the reason people have a hard time taking this argument seriously is because at least where I live when you push people a bit who use this argument a bit you realise they're saying veganism is more expensive because they literally won't consider eating beans, lentils and tofu. The only way they'll ever be vegan is by eating expensive meat substitutes that taste exactly the same as meat. They won't sacrifice any pleasure for the greater good, they're being motivated by addiction and a pathetic lack of self discipline, not logic, health or saving money. They just use those arguments because it makes them sound less sad.