Amazon doesn’t allow for Alexa’s voice to read out ad copy and no in-conversations ads are permitted in Google Actions. The companies has not yet found a way of adding advertising without compromising the customer experience.
In the case of traditional media companies as the NYT and BBC the money is not focus just yet. Other players already present in the audio ecosystem are simply using the voice platforms as a gateway to their stations. And there they already have set advertising, for instance. Another way of getting around Amazon’s ad restrictions would be to take a leaf out of The Washington Post, HuffPost, and Bloomberg’s books and make money by having the host read out the ads themselves.
Another monetisation strategy can be branded skills, so for example if a company owned a voice skill around cocktail recipes, they could make money by featuring recipes sponsored by brands.
Another way media companies could monetise in voice platforms is via affiliate sales, where users could interrupt a story that were mentioning a jeans and ask to buy them.
The most obvious monetization strategy is what’s known in Alexa as ISP: In skill purchasing, a way to sell premium content such as game features and interactive stories or sell products.
Buying these products in a skill is seamless to a user. They may ask to buy products by name, or agree to purchase suggestions you make while they interact with a skill. Customers pay for products using the payment options associated with their Amazon account.

Another way is to integrate your products from Amazon into Alexa, which works for users that already sell products on amazon.com
ISP supports both one-time purchases for entitlements that unlock access to features or content in your skill and subscriptions that offer access to premium features or content for a period of time. You define your premium offering and price, and we handle the voice-first purchasing flow. We also provide self-service tools to manage your in-skill products, and optimize their sales performance over time.

One of the challenges smart speakers have right now is more ways of monetize the platforms. AFAIK in Google this is still not possible, and the ad strategy is not clear yet in any of the platforms.

Thank you for listening.
Some monetization strategies were adapted from: Is Alexa a monetization moot?