X, formerly Twitter, has long tried to carve out a slice of the creator economy by offering a variety of monetization tools for users such as Ticketed Spaces, Tips, and more with varying levels of success.

One of its newer tools is called Subscriptions, formerly known as Super Follows, which allows users to provide exclusive content for followers who pay them a monthly fee. The feature was first launched in 2021 and renamed by X owner Elon Musk in April.

While X does not disclose the number of total subscribers to the feature, or the number of subscribers that individual creators have amassed, data obtained by Fortune regarding Musk suggests that Subscriptions is not exactly catching fire among X’s alleged 541 million users.

According to material viewed by Fortune, Musk (the most followed user on X with 155 million followers) has garnered just over 40,000 subscribers, or about 0.025% of his followers, who each pay $4 a month to get exclusive content from the tech multibillionaire. That equates to nearly $2 million annually, before Apple and X’s cut. A source familiar with the matter said that several other high-profile creators have less than 5,000 paying subscribers on X, a relatively modest number compared with their large followings.

Creators set the price they want to charge on X for subscriptions, all the way up to $250 in $1 increments, according to the source. When Twitter initially launched the feature, users were limited to setting a monthly fee of either $2.99, $4.99, or $9.99.

Creators choose how much, or how little, they give their subscribers, too. Among the menu of offerings an X creator can serve their subscribers are exclusive live audio “spaces” sessions and bonus “behind-the-scenes” tweets of their choosing.

Musk, who sometimes tweets as often as 24 times a day, rarely puts out exclusive content for subscribers. Musk appears to have posted seven times for subscribers since April, has held two exclusive spaces, and hasn’t posted since late June.

It’s not clear who has the highest number of paying subscribers on X, but premium subscriptions on other platforms can command far more paying subscribers. Top creators on OnlyFans, for example, can earn over $300,000 per month—albeit by streaming NSFW content, which is far different from what Musk is offering his subscribers. On Patreon, a platform that functions similarly to the Subscriptions feature, comedic podcast duo Shane Gillis and Matt McCusker have nearly 70,000 subscribers who pay between $1 and $50 a month.

“I think Subscriptions in its current state are a bust,” a source at X told Fortune.

Paid subscriptions have never been a cash cow for the platform. When it was first introduced as Super Follows in September 2021, the feature raked in a minuscule $6,000 in revenue, per TechCrunch. According to estimates by Appfigures, revenue by February 2022 had reached $530,000.

X’s share of the revenue is a mere 3% of what a creator earns up to their first $50,000 in lifetime earnings. Beyond that threshold, creators can expect to pocket up to 80% of their earnings. Following Musk’s rebranding of the feature as “Subscriptions” in April, he announced that the platform would abstain from collecting its customary 3% share for an entire year.

When the feature was still called Super Follows, users needed 10,000 followers and a minimum of 25 tweets within the past 30 days before they could use the feature. This prerequisite has since been scaled down to a mere 500 followers with no minimum post requirement.

X did not immediately respond to Fortune’s request for comment.