welcome to the world of mechanical keyboards. while the keyboards are far superior to your standard fare they do bring more money. the average prices range from $100-200.
remember though, if you take care of them they should last a very long time.
the das keyboards use cherry mx mechanical keyswitches i believe. i'm not sure which color switch though. the colors indicate what model of switch is used. you could try to match up the type of switch used to "no-name" or "off-brand" keyboards and get them cheaper however often alot of quality is sacrificed for the low prices so beware.
for about $100 you can get a unicomp keyboard. they are a remake of the original ibm model m keyboards of old. virtually indestructible by keyboard standards. the negative is that they are only 2 key roll over if my source is correct. this model keyboard uses buckling spring switches which are even louder than cherry mx. they are the absolute best feeling switch though and are only available on imb model m keyboards (original) or the unicomp keyboards (remakes).
in general consider them an investment that you can have for 5,10, or more years depending on how well built the model is and how well you take care of it.
i had an original model m from 1985 and another one from 1990 which although they had a hard life, still worked until a dousing in 50% alcohol killed them. i have two sets of keycaps for the model m which will fit the unicomp. this gives you the ability to have removable (and dishwasher friendly!) keycaps