no. well maybe. But no.
$171? Who was you pcb fabricator?
@trent1098s - making the board 100x100 rather than 4in x 4in will save you heaps - like $59 cheaper losing the 1.6mm off each side.
PCBCart. Wasnāt as happy with them this time - second time Iāve used them. They didnāt process the milling layer (they missed it completely when I sent them the files), so I have to carve the cardedge side out myself. 
Yeah I realized that after I got the board done and started pricing.
By then weād already locked in the form factor specs, though, for the enclosure, etc.
These are going to be plug & play modules in to a backplane in a 4U rack enclosure. So I only get one edge to place connectors, and it can be (a maximum) 6" long. The other dimension is fixed at 4" (deep). That is the physical constraints. I have 3.6" of useful space after subtracting out the .400 cardedge.
These boards arenāt the most expensive. The most expensive one to make will be the backplanes. Theyāre ā¦ large.
on card6 and beyond do the traces go through the bottom holes? 
Probably not. Canāt say for sure because I havenāt added power supply and front panel headers to the backplane yet.
If not this one I could work as a single layer board