"declining costs" is a correct and usable phrase in written English.
You can use it to refer to the process of costs decreasing or going down. For example, "The declining costs of production have allowed the company to lower their prices significantly."
April's decrease reflected declining costs of autos and computers.
And while choice is declining, costs are skyrocketing.
Alcatel's chief executive, Serge Tchuruk, attributed the improved results to declining costs.
Fundamentally, the declining costs of PV panels is better news for utility-scale solar than for residential solar.
A maturing solar industry with declining costs set against rising energy prices for fossil fuels should help.
The company, however, had also faced other challenges from the rapid improvement and declining costs of gene sequencing.
They include the declining costs of hardware and bandwidth, the wide availability of open-source software, and the ability to generate revenue through online ads.
Declining costs of apparel and computers kept consumer prices from accelerating in November, while industrial production fell for a second consecutive month, government data showed today.
The authors' tutorial on the declining costs of solar panels and power storage, for instance, makes a nearly airtight case for clean energy's imminent economic and environmental effects.
The Conference Board, which is based in Ottawa, expects that auto industry profits in Canada would rise sharply because of declining costs for labor and materials.
Globally, coal's market share is dropping, driven by a range of factors, including cheap natural gas and the rapidly declining costs of wind and solar energy.
