The actual numbers are in Google's quarterly reports as "traffic acquisition costs".
That figure bundles in the costs paid to Dell and hp to have Google the default search engine on those machines, but I think we can be pretty sure that is dwarfed by the amount paid to Apple...
Based on Q1-Q3 earnings, TAC to all distribution partners in Google's reports is approximately $13B in 2018. This is approximate since Q4 results are not released yet.
That figure bundles in the costs paid to Dell and hp to have Google the default search engine on those machines, but I think we can be pretty sure that is dwarfed by the amount paid to Apple...