i had per gb pricing in new zealand. the key feature to address your issue was that i could set an upper limit, so, say start throttling the connection once i reach $50. that's the same that other ISPs would do anyways once i reached a certain amount of usage, but with this ISP i decided the limit and i could change it at any time.
the price was competitive too. other ISPs charged $70 per month, and had a limit of 50gb (that was 15 years ago)
my ISP charged $20 as base fee and $1 per gb of usage. if i used less than 50gb, i saved money, if i used more then i could...
It's unfortunate that cellular providers don't offer this. I get around it by setting my data connection to prefer 3g. It helps with a 500mb limit (data is expensive on cheap plans), but it'd be nice to be able to throttle apps individually (no, I do not want video ads to be downloaded, but internet connectivity is required for the app to work online. A HN client with webview, for example)
years ago i came across per gb pricing but the cost was insane. it was essentially: prepay your usage or we charge you 10 times as much as the prepay would have cost you.
the price was competitive too. other ISPs charged $70 per month, and had a limit of 50gb (that was 15 years ago) my ISP charged $20 as base fee and $1 per gb of usage. if i used less than 50gb, i saved money, if i used more then i could...