Yes, a waitbar takes time to update. It looks like you are calling it a lot. And every time, it does an update. And since this is a graphics object, it takes time, serious time.
A simple solution is to filter those calls. Only update the waitbar infrequently. If I know I am going to call it roughly 100000 times, I'll skip the call almost always. Update it once every 100 or 1000 or 10000 times in your progress.
You can do that by writing a wrapper for the waitbar. It can use a persistent counter variable that is updated, but only actually calls the waitbar every x number of calls. This would be easy to write.
