This is another one of those situations where it’s unclear exactly what you’re getting with a .......”valve job”.
Means different things in different shops.
When I make out the invoice, I list all the operations that are performed.
The operations that I do to complete what I would call a “valve job”(you bring in two assembled heads, get back two assembled reconditioned heads...... assuming the heads aren’t extra grungy or rusty):
-disassemble heads
-jet wash heads
-bead blast chambers and ports
-jet wash again
-recondition valves
-machine & finish grind seats
-clean all parts
-test springs
-final jet wash
-assemble heads & set spring heights
That’s $450 at my shop,
Magnaflux and milling not included
If the heads need to be oven cleaned & shot blasted it adds $40
To do all that for $150........ someone would have to have an extremely low overhead, and have a really low hourly rate.