I think it's way better to scan it in 4K (at least) and then downscale it to 1080p, than scan it directly in 1080p... maybe the cost is around $500, but someone with direct experiences could be more precise... so, at the end, buying the film, ship it to the lab, scan it, and ship it back to the buyer will be around $1000 - not that cheap...

OR... it's still possible to regrade the BD using the (few) 35mm stills on the auction as color reference; it will be not the best way to do it, and results will be way worst than using the whole film scan, but at least it will be free! (^^,)