Just extending the hypothetical, the developer can drop the price to $2.49/mo passing on the savings to customers and perhaps capture a few more customers at that price point.
While it is true that inertia might stop many customers from changing the default, it does give an additional degree of freedom for devs.
Also, in price conscious geographies like India (where Apple just launched their first two retail stores this past week), we have alternate payment mechanisms like UPI (Unified Payment Interface) that are zero cost. So, why should a dev be forced to use only the payment mechanisms offered by Apple?
While it is true that inertia might stop many customers from changing the default, it does give an additional degree of freedom for devs.
Also, in price conscious geographies like India (where Apple just launched their first two retail stores this past week), we have alternate payment mechanisms like UPI (Unified Payment Interface) that are zero cost. So, why should a dev be forced to use only the payment mechanisms offered by Apple?