The IRS wants theirs if it's 10$ or 20k. Obviously they are less likely to notice the smaller the amount, but you can get randomly audited for some other crap and if they find 8k of gambling winning that's not reported, they will want their cut.
The 10k everyone talks about was the amount banks had to report for cash deposits (it's now only like 3).
The IRS can get any info they want, but getting a 12k wire isn't gonna throw up flags or anything. Obviously bigger is more likely to be noticed, but structuring transactions to stay below 10k is illegal. Most books can't.won't send more than 10k at a time anyway, though bookmaker/greek have unlimited wire caps.