For anyone else who was wondering, the author said the project used approximately a dozen (cubic) yards of concrete. Prices seem to be on the order of $150/yd3, so $1800 for just the concrete.
having just one seems like it's not going to help much tbh. he needs a second why to teleport to.
also not sure if concrete based gate will work... never tried that.
In the picture section (in Google Maps on Android at least), there is a video of it being lit up.
[1]: https://stargate.fandom.com/wiki/Solitudes
https://www.youtube.com/watch?v=spyhk4_USyA
https://www.atlasobscura.com/places/stargate-kappern