Usually yes — with your eyes open, an insurance answer in hand, and the replacement cost reflected in what you pay.
Polybutylene — usually grey, sometimes blue, flexible plastic supply piping — was used widely in Canadian homes built roughly between the late 1970s and the mid 1990s. Calgary grew enormously in that window, so a very large number of homes here have it. It is not rare or exotic; in some communities it is the default.
The concern is not that it fails constantly. It is that when it fails it tends to fail without warning, at fittings, and the resulting water damage is expensive. Degradation is linked to chlorine in the water supply and to fitting quality, which is why two houses of the same age can have very different outcomes.
The practical issue is not plumbing, it is insurability. Some insurers will not write a policy on a home with Poly-B, some will write it with a surcharge, some exclude water damage from it, and some do not care. This varies by insurer and changes over time.
Get an insurance quote before your condition deadline, not after. That single step converts a vague worry into a number. If a home is otherwise right and one insurer declines, another may not — but you need to know while you can still act on it.
Full replacement cost depends on the size of the house, how many bathrooms, how much of the piping is accessible, and how much drywall has to come out and go back. A bungalow with an unfinished basement is a very different job from a two-storey with a finished basement and three bathrooms. Get a real quote on the actual house rather than a rule of thumb.
Whether it should change your offer depends on whether the price already reflects it. In communities where most homes of that era still have Poly-B, the market has largely priced it in and asking for a full replacement credit will not land. Where a comparable home nearby has been redone, it is a fair conversation.
Poly-B is a reason to negotiate and to check your insurance. It is rarely a reason to walk away from a house you otherwise want — a great many Calgary families live perfectly happily with it.