Rsync.net works out essentially the same ($6/month cheaper) on a monthly basis, but offers 10% and 15% discounts for 12 and 24 month options.

B2 does mention a "capacity bundle", saying 250TB/year is $19.5K - but that's $1.5K more than the monthly pricing for the same capacity so it doesn't seem like they have any meaningful long-term pricing discounts.