Roblox spending spiraling out of control

My 10 year old somehow spent $47 on Robux last month without me realizing. I thought I had purchase controls set up but apparently not tight enough. Now he's claiming all his friends have premium and he needs it to not be "poor" in the game. How do other parents handle the pressure for in-game purchases? Should I just let him earn it through chores or am I being too harsh?