Actually, I'll expand on this before you even ask.
Taking for example this post:
Now without knowing your actual contract rate it's hard to show accurately, but lets assume £100k a year for an average IT contractor.
Sole trader:
Profit: 100,000
Class 2 NI: 120
Class 4 NI: 3,421
20% Tax: 7,200
40% Tax: 23,426
Total deductions: 34,167
LTD company:
Salary: 5,435
Profit: 94,565
Corp Tax (21% rate): 19,859
Income Tax (40% rate): 9,677
Total deductions: 29,536
A saving of £4,631. I'm also sure I've seen posts of yours where you say you're actually paying yourself more than the £5,435 personal allowance.
So yes, that's why I don't think your figures add up, and you also have the added accountants expenses when running a LTD company.