"Roedd e'n rhad."
Translation:It was cheap.
Could this also mean that "he was stingy" in the way "cheap" can mean stingy or miserly when it's applied to people?
That would be perfectly correct and is accepted as an alternative answer.
You would use 'roedd e'n rhad' if the 'it' you are referring to was a masculine noun, eg car
'Faint oedd y car?' 'How much was the car'
'Roedd e'n rhad' 'It was cheap'
The same rule applies for 'hi' as 'it'.