My brother told me to buy the cheap house paint and I regret it

He said the expensive stuff was a scam and to just get the $20 gallon from the hardware store. I painted my whole living room with it six months ago. Now it's already peeling near the windows and looks terrible. I have to scrape it all off and start over, which will cost way more in time and new paint. Has anyone else had a paint job fail that fast and what brand did you switch to?