It's not insane for self-employed people to pay that much, unfortunately.
When you are self employed your net income after expenses has self-employment taxes stuck on immediately. That's the social security and medicare tax on everything that you earned. In your case that $150,000 times 15% so $22,500 of the taxes you're paying are that.
Then the income is taxed federally. Married filing joint the tax on $105,000 is $13,715. The total on that is over $35,000 (it's been reduced because of your self-employment tax credit).
So, yes, it's about right.
@emy