In general / 50k feet terms some food for thought is , on the 10k reported in Fringe benefit value on your Mrs group certificate, her company would stump up effectively 10k in FBT tax (approximately 2 x fringe benefit value x 50%.) That value of fringe benefit is effectively what taxable income at the highest taxable rate that would need to be added to your Mrs salary (gross taxable salary) to pay for those benefits in after tax dollars. Yes the businesses can generally claim the cost of providing that benefit, as a deduction, but get dinged the associated fbt.
Unless your Mrs has say a novated lease, the company will cough up the fbt liability. If that 10k of fringe benefit value included fbt on a novated lease, her company would novated their fbt liability on the lease car to your Mrs who could pay for that in pre tax dollars (salary sacrifice). Yes the bean counters reading this will be saying what abount if not on the top marginal rate, can use after tax dollars to reduce the fbt liability, instead of salary sacrificing in pre tax dollars, but call that a wrinkle when giving a general view at 50,000 feet and not at 0 feet).
In terms of indirect impact on that reportable fringe benefit value to you and your Mrs, that numbers gets used when assessing threshold limits such as medicare levies, super co - contirubtions, low income tax rebates, private health care rebates, HECS debt repayment levels, child care rebates, child maintenance for divorsee's. Been on the end of an unpleasant WTF call on a decent ding to a child maintenance adjustment for an employee that wasn't exactly small due to an increase in reportable Fringe benefits value.
Now just a view, but fbt came in because of the baby boomers and a small minority of them earning bugger all in salary and paying bugger all in personnel income tax, but their businesses, businesses which employed them gave them access to largesse for nothing, eg fancy cars, holidays, long wined lunches, paid for kids private school fees that were free carries to the individuals and the companies were claiming those costs in full or partially against taxable income. So ATO , pollies got all bent out of shape and said to the businesses if you aren't going to put that stuff in individuals salaries that they would pay tax on and you want the deduction, we are going to ding you as if you did include those benefits in your employees salary packages and we will ding the company instead of the individual for the tax.
Aside, what many businesses don't appreciate is there are circumstances where Company Z can provide a benefit to company X's employee and Company X will have a legal liability to pay the fbt, not withstanding company X didn't outlay a cent or claim a cent and company Z claimed the cost of providing the benefit in full or in part. At times, best to bring in the bean counter sitting in the corner at times to the table when tendering me thinks. eg better to go in eyes open than not. Those FBT bills can be nasty if not costed.