To find out you could click this link, or, since that's very NSFW, you can just let me break it down for you here:
All ranges are the average for women in the industry. A given star's mileage may vary.
Per Year: $40,000 to $50,000
Guy And Girl Sex Scene: $800 to $1,000
Each Additional Guy In The Scene: $100
Anal Included In Guy And Girl Scene: An extra $100 to $300
Blow Job Only Scene: $250
Lesbian Scene: $600
But what about the dudes?
In straight porn they get between $200 and $600 on average per scene.
No dollar figures for gay porn are listed in the article.