very simple. I kinda know the prices for strats cos I buy a whole lot of em before. however, if you were to ask me for a very very rough gauge.... I would sum it up as.....
mim = $500 +/- ( depending on model and year )
mij = $500 - $1000 ( depending on model and year )
mia = $800 - $3000+ ( depending on model and year )
vintage fender stratocasters... if you do not have more than 5 figures in your bank account, I guess you can forget about those strats made in the 60s.
mim/mia/mik/mij really varies. I cant really say which is the best but I can only say that the Japan makes are the most consistant in terms of quality. of course, cannot fight with those Custom shop etc etc..... there is a reason to the pricing right?
anyway.... just do a search on the internet or on the buy/sell threads for Fender strats. see which specifications suit you best and find out the price. whether its cheap or expensive really depends on whether you are willing to pay that price for something you want.