Buy a brand that is fully guaranteed for 5 years. We sell them at 4 to 5 years old. This completely kills the repair budget.
Buy vehicles 6 months to 1 year old. That one brand we buy (like most but not all brands) doesn't depreciate linearly, and depreciate the most the first year. So this reduce the depreciation budget significantly.
The only difference in the consumable budget, compared to a 10 year old car is that we pay a lot for insurance (full vs 3rd party only).
The plus of our strategy is that an accident does not change our budgets, which it would in OP's case, as they might have to increase repair (assuming 3rd p ins) or force them to buy their next vehicle early, throwing out some of their calculations.