I'm equally sceptical. Additionally the accusation of "paid pumper" is just insult language, clearly the accuser has no idea of the motivation of any particular poster.
If you're invested, you have made some sort of calculation of probabilities of success and a good return on investment. So... you will justify your commitment, and the positive will outweigh the negative. Some people use that as "evidence" that you're a "pumper". Pretty ridiculous at the very least, and I suspect, malevolent in most cases.