How? Union? That doesn't compute either.
Not union. It's completely normal for the plumbing bill for a 1500 sqft New house here to be around $10k materials in, most expensive item is usually a high efficiency gas water heater @ about $900, the rest is pipe and connectors. Homeowner/general contractor supplies fixtures. Total material cost is about $2200, rough-in labor about 24 man hours, finishing about 8.
So pay your apprentice $18/hr (typical second year rate) @ 16 hours, that's $288 plus employee costs, so $320 about. That leaves you with $7480 for your own 16 hours.
$467.50/hour. I see it almost every week.