Is $2,000 to fix leaking roof vents a fair price?

I live in a 9-year-old terraced house, timber frame with outer brick, 3 storeys, single-pitch tiled roof with concrete capping at the highest point. There are three roof vents (two bathrooms and an airing cupboard). During heavy rain, these vents have recently started leaking. The roof has otherwise been trouble-free up to now. A number of neighbours in identical houses have already had similar issues and other roof work done. I spoke with a roofer who has worked on nearby houses and he felt the original roof work in the estate was rushed and not finished to a great standard. I'm struggling with whether it’s sensible to spend the extra money on the capping now while he’s already there, in the hope of getting 10+ years of hassle-free roof, or whether that’s overkill since it’s not leaking yet. For context, he’s done work for other neighbours where the final bill was much lower than expected because the job turned out to be quick, so I don’t get the impression he’s trying to invent work unnecessarily.