LONDON — Prince Harry and the former Meghan Markle plugged a firm offering a “transformative workout of the body and mind” that costs $42 while highlighting Mental Health Awareness Month.

The royal couple's official Instagram account, which is followed by 7.6 million people, tagged The Class alongside charities including Anxiety UK.

The post said Harry and Meghan, who is now known as the Duchess of Sussex, were “hoping to shine a light on several Instagram accounts that promote mental well-being, mental fitness, body positivity, self-care and the importance of human connection."

It added: "There are countless organizations doing amazing work for mental health — please consider the accounts we’ve highlighted as a small snapshot of this global support network."

The Class is run by fitness guru Taryn Toomey, who also organizes luxury retreats. Four nights attending one in Mexico, for example, sells for as much as $3,500, with similar retreats in Whistler, British Columbia, going for $2,900.

The Class costs $42 per session in The Hamptons. Other locations where they are offered include New York City, Los Angeles, Miami and Vancouver, Canada.

Some Instagram users questioned why Harry and Meghan had not focused the April 30 post entirely on charities.

"I think the royals do need to be careful to be as transparent as possible when it comes to what they are promoting, to ensure it does not look like they are giving friends special treatment," NBC News royal contributor Camilla Tominey said. "Clearly the impetus behind this initiative appears to be hugely positive and that should be welcomed, but any allegations of favoritism will detract from the worthy cause they are trying to promote."

A spokeswoman for the the Duke and Duchess of Sussex declined to comment on the former "Suits" actress' relationship with Toomey.

"There were no advance discussions with any of the charities, causes or individuals" tagged on Instagram, she added.

NBC News reached out to Toomey’s spokesman for comment, but has not yet received a reply. However, Britain's Daily Mail quoted a spokesman for Toomey’s company as saying it was a "great honor to be highlighted and supported" by the royal couple.

Harry and Meghan are part of the Heads Together campaign, a mental health initiative spearheaded by The Royal Foundation of The Duke and Duchess of Cambridge and The Duke and Duchess of Sussex.

The campaign aims to tackle stigma and change the conversation on mental health.

In a candid interview in 2017, Prince Harry admitted that he had come "very close to a complete breakdown on numerous occasions" because he was unable to deal with his grief after his mother's death.

The prince also revealed he sought counseling after years of "total chaos."

He recently teamed up with media mogul Oprah Winfrey on an upcoming documentary series on mental illness and wellness.

Harry and Meghan welcomed a baby boy last week.