Expense reimbursement is always tax-free for the employee and fully deductible for the company, whereas any increase in compensation from $100k-$150k can carry an effective tax rate over 50% due to progressive marginal rates and phase-outs.
Particularly for these types of ambiguous use items, I would expect savvy companies to be maximizing this benefit, not minimizing it.
The cost for an employer gets cheaper as an employee makes more money, not more expensive. There are no increasing marginal rates for employer payroll taxes- just the employee state/federal income taxes.
It depends how you measure the cost to the employer. When you're talking about increasing employee compensation in the $100k - $150k range, I look at the total cost to end up with $1.00 in the employee's savings account. The point is that increasing compensation is extremely inefficient in the $100k - $150k range. That's why, for example, US engineers getting raises in that pay range will often find it doesn't change much in their living situation. "I got a $10k raise" but really take-home pay just increased $4500.
Often times paying out compensation in cash like this is just too expensive. It's a weird concept that the cost of cash is a curve mostly dictated by tax rates. When the IRS is taking 55% at certain points in the curve, you get much bigger bang for the buck by offering other benefits, like maximizing expense reimbursements. (phone, internet, qualified commuting expenses, food & entertainment, etc.)
Particularly for these types of ambiguous use items, I would expect savvy companies to be maximizing this benefit, not minimizing it.