£10 GBP a month for a AS with an IPv4+IPv6 subnet + worldwide POPs that allow you to advertise your subnets over BGP? How did you pull that off? I've researched this a while ago and just the IPv4 subnet alone was at least 10x that amount if you are OK with leasing it from less reputable sources.
You're right, if you've got a legacy internet requirement then that adds another grand a year to your costs. But I disagree that it's "quite expensive for an indie project", especially one that's so popular it needs to run it's own CDN.