Agree with Michael Q. etc about a deal being a deal. In addition, Justin S. had a good point about reviewing your lists.
List thoughts - are you screening your out of town lists to include target neighborhoods with more distressed properties in general, rather than upscale neighborhoods where out of state owners have lots of cash and options for their properties? A subdivision or zip code review might be in order if you haven't already. You might also need to expand your geographic area so you get enough median-sales-price-and-below homes. I've had good luck with delinquent tax mailings, hope you do too.
Also - are you mailing to the same people multiple times, and do you put the ones who call you on a regular call-back schedule? I spoke to a man yesterday who told me in October he'd sold his house, but I followed up and turns out he hasn't and my offer is looking better. Keep politely checking in with them until they've sold!
If you want to post your mailer here I'm sure others would be happy to give input on that as well.
Alison