To call a Mont Blanc and a Sailor 1911 drastically different is a bit of a stretch. Visually they are almost identical, size varies based on model but the 146 and 1911L are pretty close. Filling system can vary, but the 1911 Realo is a piston filler like the MB. War are the drastic differences you're thinking of?
Well, not specifying which models you're comparing makes it less of a stretch. Look at MB's writer's editions and compare them to ... which Sailors? Look at
this Sailor and tell me which MB to compare it to. They are very different companies aesthetically.
They use different materials (MB's "precious resin" is more brittle but takes a better polish, MB's nibs use 18kt - they used use my preferred 14kt - while Sailor usually uses 21kt). While the torpedo shape is usually equated to the MB 146/149, there have been other brands/models that use it, too. As for a piston (not my favorite filling system), I'm not sure how their construction differs but I know MB has changed theirs over the past decade or two (some feel for the worse).
The writing sensation (flow, nib feel, ergonomics) are very different between the Realo and the 146/9 (whichever is closer to you); neither is clearly better but, at least to a pen guy, they are very different. Heck, there are significant differences between a 1985 MB149 and a 2014 MB 149.
In the end, why use the phrase "...and half the price of a Mont Blanc" to describe your pen? There are great writers for far less and for far more than either the PM 146/9 and the Realo. I haven't used my MB149 for at least 4 years as I have pens, both less and more valuable, that I greatly prefer.