The timing belt is treated as an age/mileage service (~60k or by age regardless of miles) that buyers demand records for; the 1.8L is a non-interference motor so a break just means replacing the belt, and the job bundled with water pump/hoses runs roughly $1,800-$4k at a good independent shop.
Timing belt: age-based service, non-interference, cost
Mazda MX-5 Miata (NA) · mechanical