the 10,000$ of deductions has reduced Bobby's tax liability by 3,250$, which is 10,000$ x 32,5% ( Bobby's highest marginal tax rate ).
As mentioned above, it is apparent from the example that the "value" of a deduction ( ie the reduction in tax payable ) will depend on the individual's highest marginal tax rate. In this case, the "value" of the deduction will be even greater as Jack would also be liable for the 2% Temporary Budget Repair Levy and his highest marginal tax rate is effectively 47%