Hey, I would be doing the same thing if I had the chance to get orchids for that price. Your plant looks pretty good! The blooms are beautiful!
I had ants nesting in one of my pots once, and I just soaked (drowned them) in water, and then took it out of that medium and threw away all the old and sprayed the roots, etc, before repotting, just like you did. Never had anymore problems.
At least this will bump you back up to the top for someone else to give you their take on ant removal.