I was quoted 500 dollars for transmission fluid flush for Volvo 

is it some thing that is absolutely necessary ? 
I saw it usually costs 250 to 300 

the dealer appears to be over charging 

What does the manual say bro? Go by that 

All these fluid flushes are over rated and over priced at dealers. Try outside dealers. Go electric. Less parts and less to no maintenance.

3 hours ago, iddaritho said:

I was quoted 500 dollars for transmission fluid flush for Volvo 

is it some thing that is absolutely necessary ? 
I saw it usually costs 250 to 300 

the dealer appears to be over charging 

How many miles ?

Most cars say no flush - drain and replace. Buy 3x the volume you need - drain, replace - drive for a mile or two. Repeat 2x or 3x ...