The prize money is obviously too low for folks to jostle for. If you have so low a budget, it would have been more advisable to make it a pay for all qualifying entries. Say pay $10 for each entry. $500 would have given you 50 entries and the corresponding publicity. To get people interested, competitions should budget up to $5000.
Hello! Thank you for your valuable idea contribution. If we decide to go for professional bloggers with thousands of subscribers earning on reviews, we will launch a separate campaign with payouts. This contest is for microbloggers. Therefore we decided to go with this offer. Many microbloggers review platforms for free to create content on their pages, increase the numbers of their followers, etc. Here, in addition, they stand a chance to win.