That's not how the math works. Travel related expenses earn 3x points. That doesn't mean that he could have redeemed his $500 worth in points for $1500 in travel. It does mean he accrues points faster depending on the spending category. For most "normal" people, I think the Citi Double Cash back card is close to ideal: 2% back.
If you go by Chase Sapphire Reserve (one of the top high-end cards), the points redemption value is 1.5x for travel. Now some of the most savvy travelers can redeem points for awards travel at even better valuations, but that depends on how you look at things. Let's say you can travel biz class round-trip for 60k points to some international destination. That's a great deal compared to what the cash price of the airfare is, but is it worth 60k points to me? No, not really if the coach fare is a lot cheaper.
Finally, as far as what purbeast is talking about is card churning. I have excellent credit and I suppose I could do this, but it's never really piqued my interest. It's perfectly legal, but if too many people do it, the card companies will get stingier. That's why airline miles/points are devalued every couple years, because a very small percentage of people abuse the system.