check edmunds.com for invoice pricing on the specific model you are looking for.
i picked mine up for $23,000 (includes destination and tint) before TTL. white cost about $150 more. don't go off OTD price because it will vary state by state.
a couple of others have been able to get ridiculously low prices (dealer giving in from holdbacks it would seem)
on average. anywhere near invoice is a good deal. I've heard though that dealers have been given a "secret" $500 rebate from mazda to get rid of all 2008 models. so you could possibly get $500 below invoice if dealer has a lot of stock.