You can get close to 50% if you live in California. They take 8% starting at about $40,000. You pay FICA on the first $132,900 now, 15.3% if you are self employed. After that limit, you still pay 1.45% for Medicare on all earned income.
If you make $140,000 a year in CA and are single, you pay almost $25,000 in Federal income tax, almost $10,000 in CA income tax, and over $10,000 in FICA. That's not half of course, but it's a chunk, about a third, and more if you are self employed.
The good news is that on unearned income, you don't pay FICA. I like unearned income, as I didn't earn it, somehow.