You don't need rep refills. refills by genuine pen companies (other than MB) will fit MB pens. I use a Monteverde rollerball refill that fits in my genuine MB 163 Rollerball. It lasts much longer than the 6 pages or so with the gen refill. That's about a dollar page.
By the way, those rep MB pens are nice, so are the rep MB fountain pens, but you are looking a pics off a genuine. I have about 10 genuine MB pens and only 2 or 3 rep MB's. To me, MB's are cheap enough on the secondary market to get gen. Most can be had for the price of a good rep watch.
If you are testing out the waters if fountain pens are for you, sure try out a rep MB. But there are as many fountain pen makers out there as there are watch makers. Lots of genuine fountain pens can be had for as little as $10. Some write extremely well. If I told you it was from a $10 pen you probably wouldn't believe me.
I just wouldn't go out making a collection of rep fountain pens though. Rep watches. . . different story.