First off, don't let those prices scare you. those are prices you would pay, buying NEW and/or buying PRO MODEL boards. There are many many boards bellow that price that will provide a significant improvement. the same can be said for boots too
I don't mean no disrespect to your current board by the word "improvement." based on my own experience and others making transition I/WE can say the improved feel of having a board (and boots) made by any reputable-brand/ major-player-wakeboard-brand within the last 5 years or so is worth it!
some companies who are not major players in making boards (ie body glove, air head, etc.) make entry-level boards, packaged and ready to shred. they are are great buy for those getting into the sport, especially if not sure about how deep they will get into it.
when it comes time to upgrade:
*Demo if at all possible. ride your buddies' board(s)
*a good pair of boots that are comfortable is a hair more important than the board you ride. if you dont have good boots you wont be able to enjoy the board they are connected to.
**** get a non stretch wakeboarding specific rope (if you don't have one) the material should read "spectra" or "dyneema" - a good rope is more important than even the board and boots. after all, it is what connects you to the boat and keeps you shredding.
Welcome to the world of wakeboarding.