When I left the bike shop in 2009 they were charging $75 for a tune-up. With prices going up on everything, $90 sounds about right.
Can you do it yourself? Sure, if you have all the necessary tools (more than just wrenches and screwdrivers) and the knowledge/skills.
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The Lord is merciful and gracious, slow to anger and abounding in steadfast love. - Psalm 103:8
I am a cyclist. I am not the fastest or the fittest. But I will get to where I'm going with a smile on my face.