Property owners decide the rent...since its their house. Its allowed because they're the owner. (Much like if you decided to rent your bicycle to someone ...or your vacuum cleaner...or your computer. You are allowed to set the value you rent it for...because it is yours).
Have you checked with a lender...to see if you could buy? Rather than continue renting? As you have figured out for yourself...at current rates...you could probably own for less than you'd be paying a landlord.