First 15GB is FREE
100GB is USD $1.99/month
1TB is USD $9.99/month
If you need additional backup, you can also consider buying cloud server which cost from SGD $200 – SGD $1000. This is a fix cost to businesses and it is a one time cost. You just need to plug in to electricity when you need to backup.
Cloud server is claimable for PIC grant from IRAS if you have fulfill the condition.