If we stopped auditing those with AGIs less than $25,000, then all I’d have to do is take enough deductions (retirement contributions, unreimbursed business expenses, medical expenses, loss from property sales, tuition, etc) to get my AGI below $25,000 and I’d never have to worry about being audited.

Ever.

One way to significantly reduce your taxes is to lower your AGI. So if anything, the lower AGIs would be a good place to start looking for tax cheats.