sterio wire harness question

i just bought my first car, a pos 87 cavy. im putting in a new head unit and i went to my local audio store and they wanted 18.99 for it. I was crusing round the internet and found some for 8- 10 bucks a piece..? im not sure if there is anything different or if its just the store.

i just bought my first car, a pos 87 cavy. im putting in a new head unit and i went to my local audio store and they wanted 18.99 for it. I was crusing round the internet and found some for 8- 10 bucks a piece..? im not sure if there is anything different or if its just the store.

It's the store. You can find most anything online cheaper