Irony

One day, I would like to go shopping but it was raining. So I made up my mind not to go because I had to go by bus. It cost me a lot. But in the afternoon, it was fine and I went out on foot without having my umbrella. When I thought I would go home, it begun to rain again so I couldn't help buying an umbrella. It cost me ￥2000!!!　If I had go out with my umbrella when it was rain, I would use only ￥320. It was an irony.