The start up costs they quote are a bit on the light side, it's likely to be closer to 6,000tl and each additional director/partner adds about 500tl.
I don't know where they get the ongoing monthly costs of 3,000tl as apart from the monthly accountants fee and a number of smallish taxes, this figure is wholly dependent on turnover.
One important point is that unlike in the UK, once you've set up a limited company you're stuck with it! Closing down a limited company is Turkey can take up to two years, during which you're still liable for accountants fees, taxes and any social security payments.
JF