Doors and Windows - Dormer doors

I recently finished our bonus room and need to finish one more project in it. I need to install dormer doors. I called around to various home stores and contractor yards to buy both doors. The cheapest I found was $98.00 a piece, and after asking about the doors they are basically cabinet doors made to fit the opening. I have no expertise in this area, but can't I make them cheaper?? The rough opening is 24" x 30". Does anyone have any suggestions?? Or has anyone made them cheaper (less expensive). My thought was to buy a $24 6 pannel door and cut it to 30"length and shave the sides until it fits with hinges ($3.50 a piece).

You might try sawing the door down to what you need to fit, the just reblock the sawn down door. Then install it.

Where would I need to reblock it at? Is a 6 pannel door hollow like the no pannel doors?

Yes, the 6-panel door is hollow. You reblock it where you 'need' to. Saw the door up. Then reblock what is left.