1996 Geo Metro I am wondering whether we were overcharged o

Electrical problem
1996 Geo Metro Automatic

Dear Bob and Ken,

"This is a classic example of what happens when a budget alternator is installed.", You sometimes said here.
My old alternator was replaced, but a part cost nearly $250. And plus $200 for mechanic's work.
By the way, I found an alternator in your website, and it costs from $90 up to $150.
Moreover, the first car repair shop, S estimated this whole work including labor, around $300.
My husband has a long term business with a mechanic in the second shop, so we let my husband's "friend"? To fix my old car at the second shop, X.
He charged us, altogether around $ 520. (Alternators $250, ALT Belt $28, test $40 and for his labor $200)
I think, we were overcharged. What do you think?
My husband let his "friend"to fix my air-conditioner, so we paid another$125. (AC BELT$30, ACDYE$15, labor$80 and so on.)
If his friend took advantage of my husband and did overcharged, I wouldn't bring my car to this shop again.
I have to search a new mechanic in my town.
Please give me your comment on this.

Sincerely.