I believe that the answer to this question really depends on the skills of the farmers to his own building/fixing, as the handwork may increase the prices.
It also depends on already existing spaces or not on a barn.
It appears that the higher cost for hygiene lock construction is related to installing a sink (the sink itself + plumbing expenses when pipes have to be added).
Some companies propose fully equipped “mobile” hygiene locks (they mey be added in front of a door) for 2000-3000 euros. Finally, apart from the sink, the equipement may be very cheap (bench, hooks on the walls, bin, …).
I have even seen on some farms hygiene locks made from recycled garden’s huts.
