^^^ As he said, price is really going to vary based on where you live and if you happen to get lucky or not. It also depends on how much time you want to invest finding that "you ****" deal...
Garage Sales & Estate Sales typically yield the lowest prices, but just finding one with a quality vise could be a challenge in itself (again depending on what part of the country / world you live in).
Craigslist and other online classified ads are also good, search surrounding areas too, it might be a bit of a drive but it will still be cheaper and better than something new.
Local auctions can yield some good stuff, but prices can be driven up depending on how many people attend and what everything thinks things are worth...
Finally you can resort to eBay... you might pay more but if you can't find anything local then it's your best option for the most variety.
4" vises are a dime a dozen and typically stay in the $100 +/- range, but you also have to pay attention to shipping. If you are lucky you can get a 4" shipped for about $100... Once you step up to 4.5" and higher shipping starts to cost $$$ because the weight & size really starts to increase.
Some brands to search for: Reed, Athol, Starrett, Parker, Prentiss, Columbian, Hollands, Yost, Rock Island, Ridgid, Ridge Tool, Desmond Stephans, Morgan, Record, Wilton, Monarch (technically a Prentiss brand), Craftsman... There are more but these are the majority...
If you are looking on eBay, these are probably what you will see the most of:
Reed's & Athol's (also labeled as Starrett's) are great heavy duty vises, if you are going to beat on stuff a lot then these are the ones you want. Athol / Starrett is typically a premium price on eBay (and even elsewhere because when people see Starrett they think precision instruments).
Prentiss is also a good heavy duty vise, typically older in age you need to check them over carefully to make sure there aren't any cracks or repairs (as you should do with all vises). Monarch was the "budget" line of the Prentiss', typically a little lighter in weight but still very nice vises.
Many old vises tend to have a split down the middle of the slide because people use that surface for an anvil (which it's not) and eventually something bad happens.
Parker's have a high arch in the jaws usually, which gives them a deeper throat to hold stuff. They too are pretty solid, but you don't want to go all crazy on them like you would a Reed or Athol. Parker's also tend to fetch a higher price...
Columbian's are great vises, usually cheaper in price. They have hollow castings so they weigh less than other brands for a given physical size. The metal they use though is particularly malleable as I've seen some beaten to death and it only mushrooms whereas others probably would have cracked under the same circumstances. They are still made in the USA.
Yost is also still making vises in the USA. You can find modern ones on eBay and local listings for good prices. They tend to have deep throats too similar to the Parker's.
I'm getting tired typing, someone else take over... lol...