An interesting idea which would, however, lead to undermining the democratic system in the end. A democracy justifies its claim to power by saying it is the will of the people (whether that's actually true or not is beyond the scope of this topic). Now imagine that only, say, 20% of the population actually go voting, as the rest simply decides to take the money (since most people realise that their vote, given the total number of eligible voters in the country, is unlikely to have any noticeable impact anyway, so they might as well grab the money) and the ruling party thus amassed a little above half the votes. How could the government claim to be ruling in the name of the people if only a tenth of the population actually supported them? It is also likely that the poor would be more incentivised to take the bribe, meaning further class divides and allegations that the so called democracy is actually just a thinly veiled oligarchy.
Another issue is then that only people passionate about politics would go voting, meaning the voting base would be chiefly composed of activists, who tend to have rather radical views on politics, and who would thus be pandered to by the government instead of the rest of the population (as they wouldn't be part of the voter base and thus would be irrelevant). A democracy would be unlikely to last under such a system, as one thing you likely have noticed about activists already is that they tend to be fanatical in their beliefs and absolutely hate activists of the opposing side - sooner or later, the party in power would start outlawing certain parties of the opposition, citing greater good and similar bullshit.
The proposition seems to be fueled by a desire to end the status quo and bring large scale changes to the system, in which it would certainly succeed and relatively quickly at that (of course how it would be changed is a different question entirely). If that is something you seek, it is probably an idea you might consider supporting. Otherwise, it should be avoided.