Hey Countryboy,
As with most things, “It depends.” Rarer and unusual breeds = more money. Are you looking for a heifer or an older cow? That can influence the price as well. If you’re looking for something to produce some milk for your table and throw you some calves – maybe for oxen – but are willing to stick with the common breeds, you could be looking at about $1000 or more. There are some old cull cows (gummers) that can be had cheap just need more attentive feeding program and they can still give you a calf.
For some folks that are really into “the family cow” and keep tabs on what’s showing up for sale around the nation try this site http://www.familycow.proboards.com
Good luck.
Geoff