The Adult Grid

$15 per month for a 15,000-prim varregion region on the adults-only The Adult Grid.  Can hold up to 100 avatars.

Can be sized as a single standard region, a 2×2 varregion, 3×3 varregion, or 4×4 varregion at no additional cost.

Extra prims are $15 a month for 15,000 prims.

Smaller regions also available.

A basic region zoned for landscape or residential use, capable of holding up to 10 avatars and up to 5,000 prims, is $8 a month.

More info here.