Thermal Edge Air Systems

I was charged a ridiculous unfair price by Maric, 300% more if you buy the part locally. Here is the fact. My furnace would not start. I called him, He came to my house and advised me that my furnace ignitor was broken and needed to be replaced. (he did not advise me that i could buy the part locally),He showed me the cost of the part is $145 dollar, then he said he usually offer 20% off but he would charge me for only $100. I was glad even though I had no idea what is the actual cost of this part. I trusted him and thought that he would give me a reasonable price. However, when i googled the part and found out that it costs only $35 to buy it locally. So I called him. He said that he did not charge every part 300% more?depend on what kind of parts and he decided how much to charge me. He said because he had the part available at the time, this is why he could charge so much to me. I was not satisfied with the answer. How could you justify 300% more for only 15 mins work? and I already pay $80 for you to come. I understand you are running a business, but it got to be a fair price, not 300% more!!!!!