I just checked American Airlines, and flight availability and airfares into Austin, by way of Dallas, for that weekend are utterly ridiculous.
Is something ridiculous going on that weekend? It isn't SXSW, I checked.
ACL is the following weekend (12-14), so that shouldn't be the problem.
If you are just now trying to schedule, the October 5-7 weekend is more than two weeks away. Ticket prices for all airlines usually soar when the window to departure date is less than 2 weeks out.
Nothing unusual, except for American Airlines pilots calling in "sick" and flights being cancelled or delayed, major work slowdown across the country..
Don't know where you are flying in from, but I have switched carriers on all my flights in and out of Austin from American Airlines to either Jet Blue or Frontier.