I'm finding this thread kind of funny because... it's a character in a game, there's really no point in being so worked up over it to the point of throwing a tantrum and calling everyone on this forum greedy.
The reason why Marshall is usually expensive is pretty simple. There's lots of people who want Marshall, he's a very popular villager, so he ends up fetching high prices at auctions.
There's lots of ways to get Marshall for free, since lots of cyclers give villagers away even when they're popular, or sometimes there's giveaways and contests for popular villagers.
20 million bells isn't that hard to make if you're determined, either. You can save up in your game, buy turnips and visit towns with high turnip prices to make a profit (people make millions really easily that way), and you can convert TBT into in-game bells, so if you keep posting on the forum (quality stuff, not rude and immature posts and no spam) you'll amass a decent amount of TBT that you can convert into the money you want in the game.
Maybe if you weren't complaining that people are "greedy" for selling a villager (that they've sometimes put an effort into getting, or want to make sure he goes to someone who wants him enough to make that effort) you'd have the money to buy him in no time.
And if you never get him? Calm down, it's a character in a videogame, not a matter of life and death.