There is no contradiction there. Everybody wants something better all the day. The only problem is how much you want or can spend. Why do you think people buy i7 and not Q9xxx? Because all of them need i7 or just because they can afford them?! Same thing here. If he can buy something better, than he should do it. 4870 is a mid-end graphic card. Usually people buy something better when they want a gaming pc but everything depends on everybody's budget. If you don't want to see my point, it's your problem.
As I said in my previous post, 4890 with OC can surpass 285 GTX.
Also 4890 has a better design, is more efficent at idle and uses just 30W at load than 4870.
So in the end he can spend more money and it will give him many gains.
As I said, this is my opionion and you don't have to agree.