Hello Tim
First let me say I do not own that planer but do know it is an excellent tool. Have a friend that has one. He has not switched to carbide but is thinking about it. The blades that come with that tool are not very good quality to start with so comparing them to carbide you will find a world of difference.
They will outlast any HSS blade you put on there for sure. How much will always depend on what you run through the planer. You will have to pay almost 3 times as much so you will have to do the math. Then you need to ask yourself about sharpening. Carbide can be sharpened. To sharpen them with a professional will cost more than HSS. Now both types can be honed by yourself. Not sure if you sharpen your HSS blades but they are easier than carbide. Big difference between honing and sharpening. Planer blades as well as jointer blades are always subject to knicks. Is carbide the answer??? That will have to be your call. They will definetly last longer, cut smooth but comes with a bigger price tag.
Depending how much planning you do can be another factor and buying good quality HSS blades maybe a cheaper answer. Good luck.