Seems cheap to me.

First, look at material costs- aluminum is not cheap these days- I
figure you get 20 parts from a 4x8 sheet- and bare material alone, in .
080 6061, has gotta be around 10 bucks per part.

Me, I lose money on anything that goes thru my shop that doesnt bill
out at at least 5 times materials.

Assume that a decent sheet metal shop, even without any cnc machines,
is going to be a minimum of $50/hr- and most are more. With CNC, they
are going to be wanting closer to $100/hr shop time, and you would
too, if you had a million dollars or so worth of equipment to feed.

An hour per part on these, in small quantities, is not unreasonable-
without cnc, you would need to shear 18" strips from the sheet, then
cut each one down into 12" wide pieces, then shear 4 more times for
the angles- thats six cuts per part.
Then, bending, then punching the holes and reaming to size (at least,
thats how I would do it for precision)

Fabbing up the angle- thats more money in material, more time in
measuring, setup, shearing, bending, and punching.

deburring- every part is gonna need hand deburring.

Then, somebody has to drive it to the anodizer, and pick it up when
its done. More time, more overhead on truck expenses, diesel, and so
on.

And I have never found anodizers to be cheap- $50 setup and a dollar
per part- thats at the extreme low end of anodizing prices- and pretty
much out of the picture in LA, with its high cost of pollution
controls, or up here in the Seattle area where I live.

In short, I think you got a screaming deal on a quote, and, unless you
were buying em by the container load from China, its unlikely to go
down by more than 10% or so.

I really doubt you could find a bid that low, up here in Boeing land-
when the average house (and nobody I know can find an average house)
in Seattle is $500,000.