In my area for the simple plain pck was 50+ and they like to do it after 20 weeks, guess u could say it just a more in depeth(sp) look at your baby you can tell more details and such
Cost depends on where you are located. A 4d ultrasound is a 3d ultrasound in motion. It a more accurate picture of the baby just in motion like a movie that they place on a DVD or jump drive so you can put it on your computer. they recommend you do it between 32-36 weeks that way the baby is big enough to see everything but yet small enough not to have their legs and arms squashed up by their face!