The general argument is - we can specifically identify talent and motivated learners/skill-possessing people, who will look for jobs. That's exactly what companies need and companies pay $5k-$10k a head during good markets for this rare STEM skill, like programming!
Problem - The people on these platforms are 70% likely to give up within 6 months or go into another field
Problem - Experience means 10x more than education to employers, especially fundamental experience
Problem - Your information on potential hires as the provider becomes outdated fast and supply-demand changes in hiring market can reduce your commissions by 50-75% in one year (as happened from 2022-2023)
I would go as far as saying these users - because they are typically earlier career - are actually worse for connecting with jobs boards/hiring than literally any random iPhone user for advertising purposes. And companies don't pay much to advertise to random iPhone users. I wish it wasn't so, but it is so according to how companies act.
If OP wants to monetise this way they should consider an affiliate programme to a CV upload or Jobs board site, it will test any appetite for hiring these people at the moment much quicker.
You could follow the Sublime Text model and basically have an honor system—if you're actively employed making more than $X, please pay us. If you're not, you're welcome to use it for free!
The Tech Resume Inside Out [0] uses this model (though not on the honor system) for similar reasons.
Another thing. There are several podcasts who have a free feed and paid one. Sam Harris’ Making Sense comes to mind with their free feed and a paid one for full access to all content. But they understand not everyone can pay. If one is unable to pay, they can simply email to ask for a free annual membership.
Pay what you want albums on Bandcamp are another example of a sliding scale. Suggested price $10, but artists can define their minimum.
I would look to reduce server costs instead. $7k/month for 2 million users seems like a lot. Do they execute your code on their servers? I couldn't really tell from their website.
Have you thought of adding a hiring feature? Where people upload their CVs, and companies search (anonymously) for talent?
There is a hiring model called PPA (Pay Per Application), or monthly fees to search CVs.
Your unique selling point would be companies are not getting hundreds of custom AI CVs flooding their application; they search for what they want, and you're helping both sides.
Good luck!
edit: grammar