A costly war.
A costly activity.
A costly error.
The new constitution, however, proved costly and unworkable, and failed to satisfy either section of the population.
The quest was very costly and altogether fruitless.
Several fine hotels and a number of costly residences occupy a plateau along the shore and the hillsides farther back.
Marble is very durable but also very costly.
You can try games you've never played before without committing to their full (costly) versions.