That hasn't been my experience with Mobike. When I had a paid membership, I got 2 hours cumulative for free over a month. Didn't matter how many different bikes I used, it was cumulative. Once that was up, then I'd be charged additional fees.
I wonder how much money Mobike makes from people who forget to lock their bikes. I've given them something like ~$50 so far because I keep forgetting to lock my bike and then don't notice until later after someone has been riding my rented bike for free for a number of hours. Once I realize what happened, I notify them, and then they lock down my account and won't unlock it until I pay up the racked up fees.
Maybe you are thinking of a different promo? Here’s the one I’m thinking of https://mobike.com/sg/blog/post/mobike-pass
This promo is for Singapore, it’s the same promo as China just in English. In this promo Mobike is offering unlimited free rides (<2hrs) with no deposit for $0.63/month. It says you can switch bikes to reset the time.
They are running this far below cost. I can’t see how Mobike makes any profit off this.
In china, Mobike charges $1.58 per month for unlimited* trips on their ridesharing bikes. Given how their bikes cost ~$100 each, and how they operate millions of bikes, they are losing massive amounts of money.
Investors have the same mentality (once we are a monopoly, we can charge more) but until then they are incinerating cash.
*Mobike rides have the first 2 hours of each trip free. If you stay on longer you need to pay. However, you can just switch bikes after 2 hours to avoid the fee.