I have not found anything of low cost that would work. What you found is low cost long term and will be effective.

I can't think of anything either.

Maybe try...
-2 layers of brick across & up - with concrete (think curbing, wall, etc.)
-dig the edge 2-4x a year to cut the invading grass roots - be sure far enough away from the blueberries, so you're not damaging their roots though
-to get neighbor interested in gardening & they might install a garden bed with deep mulch next to fence instead of grass. Maybe they like one type of plant & will begin to collect them to plant along the 240'. Offer to help the collection begin by giving a gift. There might be free plant swaps in your area to fill up the bed with daylilies or something else prolific in your climate.