The user is subsidising the tracking.
Google does not pay for the cost of the user's internet access or her mobile data plan. In some cases, the user might only need an offline map however instead she is coaxed into accessing the same map over a computer network again and again, day after day, year after year. The cost of that access is carried by the user, not Google. Multiply this cost over millions of users.
Users are paying, in many cases unnecessarily, to send tracking information to Google.
When Google coaxes a user into accepting the settings that Google prefers (24/7/365 tracking), users are not merely agreeing to be tracked in exchange for something, a price not easily measurable and thus perceived as "free". Users are agreeing to pay for the costs of that tracking, namely the transmission costs to get the tracking data to Google. Those prices are measurable, though few users might be measuring them.
Of course users are not opening an application and hitting a "send" button everyday to do this task; it is not conscious spending. They are permitting Google to do it for them in the background, using the user's CPU, memory, storage and bandwidth.
None of those resources are "free". Whilst users may have generous amounts of privacy and personal data to trade away in exchange for some perceived benefit, users did not have to pay for those "assets". They might not put much thought into whether each exchange was truly necessary.
On the contrary, users must pay for computing resources and internet access. It stands to reason that they might not wish to trade away those acquired assets where not truly necessary.