Been on all of that.
There is an open space that connects to a road and our shared Property Line (PL).
From road centerline to PL is ~125'
I would bid a 6" side sewer at no more than $40 per LF if we were already on the job, the ground was open, and there is no restoration required.
There is 5K
The other 5K is incentive to do so.
Where that Side Sewer (SS) would hit our property is maybe 6' uphill of where it stubs out of the basement, so I would be digging in shoring for a goodly portion of my part of the SS.
I have been there, this is what 80 LF of 8' build-a-box looks like, dug in all the way.
If I go the original route with a 2" PVC pump line, I can put it in at a constant depth, rather than a constant sloping grade. No shoring needed. The costs of install are about a wash when I look at shoring rental and having to hire Sam to work with me on it.
Obligatory Sam in shoring pic.
Where the extra 5K comes in is the peace of mind of not having a pump to concern ourselves with.