In economics, compensation to employees includes all payments made to or on the behalf of employees. So it includes the cash value of any perks, payments into retirement vehicles, health insurance premiums and FICA payments made in the name of the employee. In theory, employers (as a group) react and make decisions based on the compensation. In theory, so do actual employees and people looking for work. In theory, the extent to which employees (or employers) bear the burden of these non-tax payments depends on the sensitivities (i.e. elasticities) of the demand for labor and the supply of labor to compensation. For example, in theory, if the demand for a specific form of labor is relatively insensitive to compensation while the supply is sensitive, then the employer will end up "eating" most of the non-cash benefits (i.e. wages are not much affected) because of labor market dynamics - even though individual employers may not notice this. On the other hand, if the supply of labor is fairly insensitive to compensation, then wages will be affected by the non-cash benefits. This is a direct application of the partial equilibrium analysis of the economic incidence of a tax (just think of the non-cash benefits as a "tax").
T