Sewer connection - disproportionate costs

Hello forum,

we have privately acquired a plot of land. A right of use for wastewater is registered with the neighbor. In advance, we asked the municipality how and at what cost a connection to the wastewater network could be made. We received an email stating that approximately 14,000 to 17,000 euros net would be due OR the pipe could be laid over the neighboring property (hence the registered right of use). This would probably be significantly cheaper. Now, since the mayor seems to be obstructing and only wants to allow this through public space, the office apparently gave in and discarded option 2, quoting a cost estimate of 20,000. Are there any experiences or ideas on whether one can oppose this? Especially since it was previously said that a pipe could also be laid over the neighbor (by email and also by phone).
Perhaps a private septic tank would be possible/sensible given these costs?

Thank you!

so how much does it cost at the neighbor? here you also have to have everything restored as it was or is it undeveloped?

Plans would be good.
And length specifications.

Depending on the situation, 20K is not that unreasonable. For example, if a pump becomes necessary.

Now, after the mayor apparently is obstructing and only wants to allow this via public space, the office has apparently given in

What stake does the mayor have in the whole thing? Why does he not not care and interfere?

Thank you for the answers, it would probably be around 20 meters without a pump. Why this interferes, no idea. The office itself had said on the phone that the costs could be disproportionately high. After the veto from the BM, however, probably not anymore....