[actsasbuffoon]

I think it's a matter of etiquette and professionalism. I don't get huffy about minor misspellings most of the time, but this conversation took place in a professional context. Imagine a scenario where you discover that several thousand dollars are missing from your bank account. You don't want them to reply with, "lol, sry bro... much stolen funds, wow fraud... we'll look into that... l8r"

When talking with friends I'd probably find that kind of banter (when used in moderation) to be amusing, but I expect a business person to take the time to proofread and spellcheck a message before sending it to me. I'm paying them money, they should show me a little courtesy.