A battery pole saw is about $350. Plus batteries.
A hydraulic saw is about $1,500-2,500 depending on how nice of one you want. Plus hoses.
If he needs to cut all day, you could maybe make the case for hyd.
If its just to trim up some fence rows occasionally, sure looks like battery is the way to go. And I'm not a fan of most battery tools.
Now if it was me, I'd cosy up to the local rural electric cooperative guys, and see when they are getting new saws, or if they have a old one sitting on the shelf. $4-500 might buy a pretty nice used one.