The phrase "costly cost" is grammatically correct and can be used in written English.
It is often used to emphasize that something is expensive or has a high cost. You can use it in a sentence such as "The renovation project turned out to be a costly cost for the company." This sentence indicates that the cost of the renovation was high and had a significant impact on the company's budget.
The cancellation of "Luck," one of HBO's most anticipated and costly dramas, cost Time Warner $35 million.
But the building of the models was costly (having cost around £13,729) and in 1855, the Crystal Palace Company cut Hawkins's funding.
The failed 2001 02 Serie B campaign was costly, the cost of production was €70,895,838, just about €10 million fewer than in 2000 01 Serie A, heavily due to the high amortisation of the player asset (€33,437,075).
Further enquiry from the legal fraternity and children's rights groups revealed that the process was both lengthy and costly (estimated cost of USD100 excluding legal fees).
Although the design and implementation of such policies is costly, those costs pale in comparison to the costs of inaction.
Following this up by tearing apart Medicare, a costly but cost-effective program that has served seniors well for almost fifty years, would surely be a privatization experiment too far.
Failure during operation can be costly, including costs linked to loss of service, property, or human life.
Use of this new metric for evaluation and optimization of energy conversion processes can prevent the situation of energy-efficient but costly or cost-efficient but energy-inefficient.
Large-scale reforestation using native seedlings is extremely costly, with costs ranging from $15,000 ha−1 for bare-root stock through to $35,000 ha−1 for container-grown stock (Davis et al. [2009]).
This is not going to happen unless we burst that intellectual bubble [that mindset that says green is costly NOT cost-effective].
