If say a load of us on this forum planned to invest 1k each into an altcoin. Say burst. Would we drive the price up at all or would it take millions to drive it up enough to make a profit?
that is what the "pump groups" do. although it is not "a load of people" and just a small number of people on top who have a load of sheep following them to get dumped on.
and to do that it depends on how many sheep you can get to follow you and what altcoin you want to pump. if it is a small altcoin with little volume and very thin orderbooks then it can be done with small amount of money, sometimes even less than 1
BTC to get it going.
but if it is a bigger altcoin with a high volume and packed orderbook and specially if there are other pumpers on it then you can't do anything because they will crush you.