Ant,
Good topic for poll this time of year. Before everyone starts the bidding, make sure you note how many passes you intend to make per property. I usually get $13 per thousand square feet for 1 pass and $20 per thousand for 2 passes. These prices will definately go up if there are hills involved or if there are a lot of nooks and crannys to deal with. However with this said and one week of aerating under my belt (which is now very loose) I am upping my prices a bit. Seeding is $3.50 per pound applied.
By the way - I HATE AERATING - I just wish it wasn't so good for the lawns.