2017 Pub 15a, page 22, the gross up amount is taxable wages, including FUTA wages, SS wages, and Medi wages, so likely SUTA wages as well.
So for 100 net, the gross (and taxable for all purposes) is 108.30. Providing the employee the extra 7.65, cost the employer 8.30, plus (at least) the increased WC, FUTA, SUTA, on the 8.30. In CA, using the default SUTA, and a low WC, the gift of the 7.65 has a real cost of at least 9.