A player martingaling starting at 1mbtc and getting to 1btc is no different than a player coming and having their first roll be 1btc. Both are exactly the same. The user's previous bets have zero impact on the future bets. What people are describing here is a pure sign of gambler's fallacy. If it's +EV, it is whether or not there are bets before or after that one. It's pure math.
No, both aren't exactly the same. Assuming the player is martingaling with a 2x multiplier on loss, they would have a total of 1.023
BTC wagered before having the system up the bet to 1.024
BTC. A total of 2.047
BTC would be wagered, assuming he kept losing until the 1 BTC bet. With 2
BTC wagered, the house edge paid would be higher, and should increase the investor's chance of profit. For an investor's point of view, the martingaling person would have paid 0.004
BTC to make those bets, while a straight 1 BTC bet would have only paid 0.002
BTC to the investors (assuming the house edge is 1%)
We can't take into consideration anything but the 1 BTC bet, which stands on its own. The rest is all situational and you don't know what happened: they could have busted on run #1 (site a wins, MP wins), they could have tripled up first (site a loses, MP wins), they could make it and stop (site a loses, MP loses). Because of this conditional setup, you can only take into consideration a single bet: the one that would have been on MP regardless.
If someone goes to BetKing and bets 1 (lose), 2 (lose), 4 (lose), 8 (lose) and then stops and comes to MP and bets 16, should MP have said "no bro, you were on BetKing before and they got all your losses to this point so you can no longer play here?" That's essentially the same scenario, just a bit more of a hassle on the player's part.