The last time I checked, the link for specs and prices for the MAMBA and the MANTIS was broken. If you check under the "PRODUCTS" tab, then "PARTS", you can find the specs for each kite. No prices though. For that you will need to talk to Ken. Unless the prices have changed, a MANTIS std is about $280US.
BTW the kite pictured to the left for my avatar is a custom coloured MANTIS back lit by the sun. It's a beautiful thing.
If you just started looking at BMK, and are serious, you better start working on the colorizer now! That way you might have a colour scheme nailed down by next spring.