Basically put, your 30€/h (I assume came from 60.000€/year salary), is factually 110,000-140,000 €/year cost for your employer. It does not take into the account the financial risks you pose to the company (long time sickness, social financial obligations, ..). Second thing, the 150€/h you quote, is not going into the pocket of the freelancer. Unlike you, they’re taxed similarly to your employer, hence -21% VAT, corporate taxation, - business costs and expenses (from office rent, lawyer and accountant fees to the public transport that your employer reimburses you, simple insurances will add up to ~1-2k/month..), - social security tax and lastly the income tax. As a self employed, you are in a different pension system (read: minimal). You’d need to save that money yourself. You’re not always employed, nor paid when you’re ill, and government won’t pay you a dime if you get laid off.
If you do the math right a 70k/year salary translates to a 100€/h (excl VAT) zzp position and 130-ish €/H BV construction. Yes, it seems unfair to you, but that’s a choice you can make for yourself.