Getting an average of 50x for every bonus round is in fact not bad, I already reached too many bonus rounds on other slots where I only received 5 -10x.
The slot you were playing probably was a medium / low volatility slots that gives a decent amount of bonus rounds but it doesnt really pay off that much. Low / medium volatility slots are good if you are playing with high stake per spin but if you are only playing for less than $5 then. Alot of streamers usually spin $50 - 100 per spin on these kind of slots.
I'd say high / extreme volatility slots might pay off better ( if you are lucky
)