The part of the sentence "which is expensive" is correct and usable in written English.
You could use it in a sentence like, "I purchased a watch which is expensive."
This is lost production time, which is expensive.
Yet shorter shifts require more staff, which is expensive.
A close second is the Dungeness crab, which is expensive, messy, exhausting, and wonderful.
Mr Ghosn hopes to avoid actually sacking workers, which is expensive in Japan.
"There is high-quality restoration work, which is expensive, and which you don't see very often.
When things get buggy, they'll flood the phone lines, which is expensive for a bank.
Some local authorities refuse to stump up for residential treatment, which is expensive but works better than community care.
The increased energy demand is met by reserve energy generation, such as oil, which is expensive and polluting.
"She doesn't have the money to send him to a Brazilian school, which is expensive," Ms. Cohen said.
Israel makes widespread use of low-volume irrigation such as drip-feed and micro-sprinklers, which is expensive.
Relief supplies, including vaccines, must be transported by air, which is expensive and still not safe from rebel missiles.
