My standard paper rate is around 25-30 a page. And that can up to double depending on the topic and the bibliography requirements. Due date is also a highly important factor, if you really need it within 8 hours and it has to be totally original, you are gonna be paying big bucks.
Psychology is a pretty tough subject if its in-depth(Fruedian slip, metacognition), but a basic psych paper can be pretty easy to write (Differences between men and women thinking, subconscious desires etc.)
Give us a little more information on what you need done and by when.
Also- unless you plan on actually paying upwards of 150- you are pretty SOL for a decent paper. I used to write Intro to english papers (you know- best mentor, introduce yourself) for $50, but those were a week's notice.