If you are using the lowest cost storage tiers in the cloud there is a very good chance that you are still storing your data on tape, just not on your own tape. These cloud-based solutions can make good sense financially for storing a second copy of archive data or for smaller companies with multi-terabyte data sets.
However, if you are a data-driven organisation that is archiving petabytes, then it is going to cost much more to store it in the cloud than in an on-premise tape library - especially if you are pulling information in and out of the archive on a regular basis.
Remember to consider egress charges, bandwidth costs, and time to get data over the connection to the cloud when making these comparisons.
Cloud egress costs are expensive if you need to pull data in and out of the cloud on a regular basis or, in a worst-case scenario, where you have to retrieve all of your data from the cloud. This doesn’t even take into account the high cost of the necessary network bandwidth needed to move massive volumes of data in and out of the cloud or the long time it could take to do it.  And, tape is still the single best way to quickly restore after a ransomware hit because data is stored completely offline.  Onsite tape that an organisation owns and manages is the least expensive way to archive large volumes of data and, while this nearline data might take a little longer to retrieve, the latency time is minimal depending on the tape library.
You can find a TCO calculator on the LTO consortium website that will help when comparing potential costs of different solutions.