If DTAG asked for 1 EUR/Gigabyte, would you still maintain that position? 10 EUR? 100 EUR? Is there any point where you would consider the behaviour of DTAG inappropriate/unfair?
BTW, nobody is denying that they in fact are an important ISP, where "important" means "lots of customers", which in turn means "lots of power". Someone holding a gun to your head also has a lot of power and thus is important to you - but power in neither case automatically implies that any offer the powerful party is making is a fair offer, be it that they ask you to give them all your money to avoid being killed, or that they ask you to pay massively above-market rates to avoid being unreachable for their customer base.
BTW, nobody is denying that they in fact are an important ISP, where "important" means "lots of customers", which in turn means "lots of power". Someone holding a gun to your head also has a lot of power and thus is important to you - but power in neither case automatically implies that any offer the powerful party is making is a fair offer, be it that they ask you to give them all your money to avoid being killed, or that they ask you to pay massively above-market rates to avoid being unreachable for their customer base.