Every stock I purchased was $450 commission fee. The broker would cald me 3 weeks later and say it was time to sell. When I sold it, I paid $450 commission fee.
I hate these types of examples. Were you trading 100k worth of stock of 5k? When he called you in 3 weeks did you have a big profit? Did something materially change in the investment? This is all important.
Paying $900 round trip seems high but if it was on 100k it's less than 1% if it's on 5k it's nearly 20%. Makes a big difference.