I've managed a quote from PCBway for this board: including parts and assembly, it would cost $138 for five, which comes to $27.60 each. That's not terrible; there are FeatherWings on the market that cost more. I wish it could be lower, though.
The total component price is $88.20 -- $17.64 apiece, not counting the board itself.
(For comparison, the BOM at Octowing tells me I can get all the components for $7.75 going with the lowest overall price, or $14.43 if I get them all from Digi-Key -- in both cases not including shipping.)
The real killer is the DAC8571, which runs $5.25 per unit (online prices run $3-6 apiece). That's almost one-third of the component price, and almost one-fifth of the overall price!
At $3.88 on their BOM, the MCP3422 isn't much better (though prices I've found have been in the $2-3 range).
I'd love to find something less spendy for the DAC and ADC; and, like I say in the Description, one chip to perform both functions would really be ideal. Any recommendations?