Will raising my repair prices lose customers?

Some, yes — and the arithmetic usually still favours the increase. If you are 20% under your target rate, you can lose a meaningful share of jobs and still finish ahead, because the jobs you lose are disproportionately the price-shoppers who consume the most time per rupee. The practical approach is to raise the rate on new work first, keep existing quotes honoured, and watch the effective hourly rate rather than the job count.