Just one map though.
I mean I know that Hards give you more than insanes but there are several reasons for that and people always turn the blind eye towards that.
To get good pp you need to play maps which have the following:
1) Scoreboard which contain people who have decently high rank, preferably higher than yours, if really high rank then it would give you more pp if you beat that person
2) Good playcount. Some maps give crazy amount of pp just because of playcount.
For bonus points, the higher your accuracy is, the better your pp gets. That's pretty much all there is to it. It's really no shocker that extremely hard maps don't reward that much pp, just because of the above reasons.
For pp to work correctly, all players must play all maps and be on the scoreboard. Only then it gets really damn accurate. I thought this was obvious.
As for pp farmers, since this is the topic, they have every right to farm. If you don't like it, beat them. That's all there is to it. Sure they can suck on some mildly hard insanes, but they still perform better than you on other maps, which is the whole point.
Just as Silynn said, Hards can only get you to a certain point, to progress further you need to be good at insanes too. Obvious proof is ShadowSoul (or Sette) vs thelewa.