The comparison between Montblanc and Rolex is a very good one. Both make high quality items that have become publicly recognizable benchmarks, backed by strictly controlled supply and advertising. They both keep their value relatively well because of how well-known they are. And while both of them are well-made and safe choices, they face competition from less known brands that can offer similar features for a lot less. The issue is more with the market than the brand; most watches and pens are easy to find at a discount, but both Montblanc and Rolex are rarely discounted.
As for the pen itself, I have a 149 that's served me very well over the years. There aren't really any other oversized piston filler pens out there with as rich of a history. I also own the Pelikan M1000 which is another favorite and a great value for the money, and my favorite nibs are made by Sailor. But there's something that makes me keep reaching for the 149. I think it's kind of hard to understand without owning one, but there's a certain gravitas to their pens.
On a side note, I didn't realize OMAS was gone. Good riddance, their pens were absolute garbage. I owned an Arte Italiana from them that had the piston fall apart within a week. OMAS took 6 months to send me back another defective pen. Even without those issues, the design was terribly unbalanced, the machining was rough and unfinished in places, and the plating on the nib was all over the place. The cap didn't post because it was poorly designed and they cheaped out by putting a compact sized nib in an oversized body. I have no idea how they were able to charge as much as Montblanc for a product so poorly made.