First off, the company wants an easement for a fiber optic line, not a tower. The tower sounds like its already up. I have written hundreds of easements for my job, and most of them are signed by the owners for free. Most of these easements are for public improvement projects that can help the land owner, such as sewer and water, so they normally don't get paid for the easement.
I have also written easements for utility companies that are paid for, and it depends on the length and location. If it cuts along the edge of the property out of the way, it doesn't really hurt the value of the property very much. If it goes through the middle of the property, then it hurts the value quite a bit. I have seen these easements go for a few thousand dollars depending on the length down to a few hundered dollars.
A couple of things that should be in the easment. Crop damages, if they damage crops putting in the line, you get paid. Field tile and fences, if they damage anything, they fix it. Idemnification(sp?), if anybody gets hurt or any damage done while they are installing or maintaining the line, its not your fault and they can't sue you.
Something you can ASK for, but might not get, if the line is in your way in the future, they have to move it. Say you want to build something over the line, or some other improvement in the future, they have to move it at their expense. Easements we write for a local phone co-op have that clause written in it. This means it can never really hurt the land owner, because if its in his way, they will move it. You could take a lot less money for the easement if they will put that clause in it.
Good luck.