Ads are costing you more money (in a less directly-obvious way) than a subscription would, while providing less value to everybody down the chain, because of the cycles & network traffic involved.
Adtech is basically a form of gambling (with inflated expected odds): one party gives an estimate of how likely an impression is to turn into a sale, and pays some fraction of the product of that estimate and the revenue from a sale in return for an impression, but because ad effectiveness is mostly a function of novelty, the actual likelihood that this estimate is chasing is in a constant state of free-fall. Targetting stepped in as a way to increase the likelihood that ads are effective, but targetting really turned into its own internal market, only tangentially related to serving ads (and the only source of cash it's likely to continue to have is in the form of non-advertisers who want specific information -- for purposes of law enforcement, blackmail, training data for statistical models, or some combination of the three).
So, ultimately: you are paying the cost (in power, in bits transmitted, & in time) to see ads for things you don't want, and then paying the cost (in power, bits transmitted, and time) for information about you to be sent to a third party market in personal information, and in the end the person who paid to show you the ad isn't getting anything out of it either.
It's more cost-effective in most cases to just eat whatever it cost to develop an app or run a site than to host ads -- but, since those costs are foisted upon the end user in the form of device lifespan, it's not often done.