I have one of those, $30 is an awesome price. I paid around $70 for mine from Justjap.
Excellent gauge too, very pretty especially at night. Little hard to see in the day but its not too bad. Switch off the engine and it goes completely black, very cool.
I got the turbotech boostcontroller too, a gauge is a must have. Without it you can only guess what PSI you are running on the stock gauge, its hopeless to check of small PSI changes so forget about adjusting your boost controller without an aftermarket gauge