prices vary quite a bit depending on quality level and on the person selling them.
prices seem to average between $50-100 in the usa with a few going over that amount. i paid $130 for a pristine cleaned working model with zero damage a few years ago. prices vary... not much i can say besides check once in awhile.
ebay is your best source for the keyboards. clickykeys was selling them at higher prices and is pretty much sold out of the good ones.
a note about pckeyboards (the brand new model m's). these are made similar to the originals but are not quite as heavily built. they dont feature the quick disconnect cord and feature one already built in. personally i dont find them bad but they aren't quite the same as the originals. if you want new and perfect condition though this is pretty much the only way to get them. expect to pay at least $100 for a basic model.
the most important thing to remember when buying them is to have one that has a working circuit board, plastic sheet membrane and non-scrached ribbon cable (circuits are printed on the face of it). you can replace individual keys, keycaps and the outside case if you need to.
in fact... i have two dead model m keyboards laying around that could be used for parts. that is two sets of keycaps in great condition, some excellent quality cases and various springs and internal components. i have the long cords that plug in too. i'd like to get rid of them but haven't felt like putting anything up on ebay yet.
they really are hardy keyboards... the only reason my last one died is because someone dumped a whole glass of 100 proof into it! i still believe that they are the best keyboards to be typing on and that they will outlast any normal keyboard.
the only thing to remember is that they are only 2kro. as long as you are okay with that... its a great keyboard.
thats about $usd 176.... i know they go for about $110-120 or so new from unicomp and the shipping (especially international) can be high due to the weight of the boards.
i dont know what you're trying to get at with the price... new boards from unicomp go for a set price. old boards from ibm go for varied prices. shipping is going to be high no matter which you choose since they weigh 3-5 pounds or so. shipping via ups or fedex is going to be extremely high. shipping via usps or mail carrier is going to be much lower.
lets put it this way... shipping from japan to the us fedex wanted $600 for 2day air and 5 day air ems (jpn post) was only $60. if ordering from the usa see if you can get it delivered via usps or other mail carrier instead of ups/fedex/dhl.