Cost of drainage easement

So...I am currently in negotiations over purchase of a stormwater easement down a boundary to try and make a small development site viable for someone I know. There are some wildly differing opinions about a sensible cost to pay the neighbours.



I am also trying to make sure everyone is well educated and informed, and no one feels rushed. Does anyone care to comment on:



1. A "rough" guide for common prices to run a stormwater easement (I know the person wanting to develop will be up for actual costs, I am talking about the consideration fee to pay the neighbours.



2. Any really simple guidelines for all parties to read so everyone feels comfortable about the process.



Thanks.

Cost of drainage easement