You will incur credit consumption for storage. This help topic provides all the details for the credit costs/consumption for various types of content: https://doc.arcgis.com/en/arcgis-online/administer/credits.htm
Using the computing power available to you from ArcGIS Desktop to create tile packages minimizes credit consumption for publishing hosted tile layers. Although credits are consumed for tile package storage, once a tile package is published, you can delete the tile package item to further minimize credit consumption.
One thing to consider is publishing your content as hosted feature layers. HFLs offer a lot of additional capabilities (e.g., they are "smart," can have have configured pop-ups, can be styled in various ways, etc.) plus their storage cost is far less than creating and storing the (potentially massive) amount of tiles for high-resolution, multi-scale maps.
With improvements over the years to hosted feature layers, I've been going back to my old tile layers and republishing them as hosted feature layers, gaining lots of economies WRT storage along the way plus additional capabilities including no-brainer performance and "intelligence" and other capabilities inherent to HFLs.
Another option is to publish as vector tiles, which do have a lower footprint storage-wise when compared to map tiles. The current disadvantage of vector tiles is that they are inherently "dumb" like map tiles in that you cannot configure pop-ups, etc. But they can be styled in a variety of ways and support rotation and other "modern" capabilities. Case in point - all the former Living Atlas map tile basemaps were abandoned in favor of vector tiles, which makes update easier and delivers additional capabilities.
Where it me, I would explore hosted feature layers as the best way forward. If you are an enterprise user, then using your own infrastructure/servers is the way to go unless scalability/demand dictates otherwise.
