On adult these days backlinks from sites like the mrporngeek or theporndude are very good, and usually hardlinks or blogpost on adult sites are very expensive if comes from hq sites, and usually there is a annually fee, so if the link is for lifetime and you go with a site for long run, then 1k is nothing.
People say to get your site up to get listed for free on theporndude, yeah, the guy will list your link but not for free, you need to give link back, and this works only if your site have good stats. And when you give back link you lose some juice.