Well, please remember there has been 5-6 years of inflation since the Terminators were new.
The dealership I work for has a brand new 2010 Mustang GT with the 3.73 axle package on sale for $28,151 (MSRP is $29,340) - and that's without any kind of Ford rebates. Once Ford starts offering rebates (after most of the new 2008-9's are sold out), then you'll find base GT's in the mid $20's regularly.
I'm waiting for the 2011 with the EcoBoost to go for low 20's new and mid-teens lightly used.