So you are assuming the instaminers haven't manipulated the market to get cash? Because there's no way they could sell at artificial highs and then dump and then buy at the lower price and then support a new high--I mean that's like impossible or something.
And that's not considering the easy scenario: greater fool enters (let's say his/her name is Wodger Der), keep selling to Der, but be sure not to dump too hard and keep the all time high at a level for more than a week without a dip (because that's natural).
Or better yet, hodl all your instamine stash, collect fees, then buy more masternodes, and since you have a huge monopoly, just let the price rise on factors normal to markets and never sell--you fees go up and you keep getting more nodes and you can control the market price by not lifting a damn finger.
Or better yet, it doesn't matter how it got there, all the instaminers need to do is hodl to keep the price up--it's called limiting the supply. Now, what gets interesting, and was my point, is if a new coin has better features or offers a more fair path to distribution and has the same market focus--do the masternode holders panic or get greedy and go to the next coin? I'm betting they do and Evan and Der will burn their funds trying to fight it, until they can't.
I bolded the one that I personally believe they are doing.
This one works better if they keep the price high and steady and don't do any big dumps and just sell off their masternode earnings for profits at a steady rate.
My personal opinion is that they keep the price high by developing the coin and doing marketing and other things to make it easier for new people to adopt and use the coin all while their master nodes are tying up liquidity.
It does not benefit them to destroy the coin.
I personally dont believe they are trading between themselves to keep the price up as this ultimately costs money to do.