Cheap 4 digit 7 segment display driver
The cheapest solution may be a microcontroller programmed for that purpose.  



This is all you need: displays, a couple transistors and resistors. Should be possible for about $2. If you really want to control the colon you need a fifth transistor. (If it's always on you can leave it out of the microcontroller's way, and simply connect current-limiting resistors.)
(following Geert's suggestion) If you don't use the decimal point LEDs you can use the "DP" signal to control the colon LEDs. In that case the 4 transistor suffice.

The nice this about this approach is that you can make it an intelligent display which you could control via its UART. Of course if the application is rather simple, like a digital clock, you can put everything in the same microcontroller that drives the display.