I'm no tax expert or math whiz, but I'll take a crack at it...
Where are you getting the 30% tax rate? If your tax rate is that high, you likely don't qualify for an IRA. Your effective tax rate is highly dependent on any other income and will be less than the tax bracket you might fall in. That is because your income is taxed in tiers by the IRS. In 2013, for single filers, the first $8,925 earned is taxed at 10%. Income from $8,926 to $36,250 is taxed at 15%. $36,251 to $87,850 is taxed at 25%. And so on. Let's say my adjusted gross income is $75k for the year. Subtract the single standard deduction of $6,100 for a taxable income of $68,900. Looking at the tax tables, my tax is $13,160 making my effective tax rate less than 18%. I'm not even going to get started on state taxes as I am in a different state.
Charge-offs = capital loss and are used to offset capital gains. If there are no capital gains, then they are essentially subtracted from your income to give you your AGI. Capital losses are not taxed.
Let's say I received a W-2 for $74k. I add my $1500 OID interest income. I fill out the Schedule D, with my $500 charge-off/capital loss. That brings my AGI to $75k. $1000 net gain x 18% tax rate = $180. So after taxes, I made $820. Divide that into $10k, and my after-tax return is 8.2%.