IIRC, you were happy with the rate you agreed and said that for three days, you would earn more than you usually do in a month - that to me does not suggest you’re undercharging at all.
I do charge for travel time if it’s a holiday booking but this is factored in to the overall fee. However at the same time, if I get my own room and know I’ll be sleeping alone, then I do charge slightly lower fee. We all have different rates so it’s irrelevant really what others charge really so long as you’re content.
PS. To echo others, be careful in the cove, I suspect that while it might be hidden, it’s not so secret!