I can only talk from past experience but yes, for me it was extreamly profitable. However it's a 24/7 operation and like many other types of business it has a break point that exists between running as a sole proprietor and as limited company with staff.
If you can survive the break point and make the progression while remaining professional then the profits over time are really very good.
The only caveat to that is I'd say the current market appears to me to be rather saturated so you would probably need to specialise to gain a foothold i.e. provide a platform for a product that nobody else thinks is profitable.