US domestic flights in F on US/AA are one of the cheapest ways of picking up tier points, though obviously dependent on you already being in the US. Flights > 3000 miles get 210 TPs in F, and flights < 3000 miles earn 60. I'm doing LAS-PHL-DCA in a fortnight and earning 270 TPs on a £300 ticket (which I needed to fly anyway).
As already mentioned, however, reserving bulkhead seats will cost less than even the best value TP run.