I'm not sure if I understand the question correctly but if you are referring to requiring backup beyond the included point-in-time restore period then you always have the option of using long term retention to create a backup policy of your own and retain the backup data for much longer (up to 10 years).
Pricing is based on amount of data stored and retention period, i.e. GB/month - see here for pricing: https://azure.microsoft.com/en-us/pricing/details/azure-sql-database/single/
The Azure pricing calculator can assist you with estimating your costs - https://azure.microsoft.com/en-us/pricing/calculator/