Considering the profit margin on bikes is relatively low and most profit is on service and accessories, nothing. We are not talking about mark-up on a new car.
As a courtesy, many bike shops usually offer a 6 month free tune-up to adjust stretched cables.
The bike shops I frequent are not cash fat but hanging on to survival against internet sales.
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Road 🚴🏾♂️ & Mountain 🚵🏾♂️