Being an avid archer, I've had several opportunities to buy arrows.
Arrows that are anything more than total crap need to be custom made. (At minimum, this means cuttnig to the right length, for aluminum / carbon fiber arrows.)
Cheap arows are ~$40 a dozen,
most arrows are ~$60 a dozen (this is what mine cost),
high-quality competition-grade arrows cost $80-$120 or so a dozen, or MORE.
What would a Shadowrunner use? I think it's safe to say that the shadowrunner, because he has TIME constraints on his firing (as opposed to the olympic or competition shooter) will not benefit significantly from the uber-expensive $10-each arrows, but will still spring for the mid-range arrows. (BTW, $60/dozen is about what most custom wooden / traditional handmade arrows cost, too -- a reflection of the effort that goes into them.)
I think it's safe to say that arrows fit for a runner would be of the ~$5/arrow variety... and I think I read once that 1 nuyen was about 4 or 5 current US dollars... (forget where I read this, tho ... I think it may have been Raygun's site discussing gun prices

)
So, I think that

1-2 per arrow is about what you'd pay. 10 is Right Out, to steal from Monty Python.
Edit: Runners might actually bew more likelly to use the more expensive (~$10/each) carbon fiber arrows: they have smaller diameter than aluminum, and have much better penetration (in hay bales and other targets) than the other types. When you consider most runners would be shooting at armor ... penetration is good 
Also edit: yeah, what toturi said. 
Of course, any archer that is shooting at COMBAT targets more than 20-40 meters is either godlike (if they hit) or unlikely to hit anything... most bowhunters (who have the element of surprise
) do most oftheir shooting from 20-25 yards. Or so I've read. Though, partly that's so that they can ensure a clean kill...