Even putting aside Miles Austin's contract, Beasley has more trade value than Austin. More teams would be interested and can use Beasley than whatever they could do with Austin.
The only reason Austin is even on the team is because it would have cost more to cut him. But, hey, maybe he can help the team down the stretch and if someone gets injured, it is not too bad having Miles come in.
If you think Free's paycut-or-else was huge, wait till you see Austin's offer this off-season. A little over vet min with some incentives. And even though it is the best offer he gets, he still leaves because he thinks he is a starting caliber WR and goes to Jax or Clev for a one year vet min contract.