The problem is cost. I've done about five of these. The promotion will land you more than any other promotion out there in sales, but $500... ouch. This is not a standard BookBub. You're not gonna make your money back and you're not going to sell 1000s of books. If you do the promo, and looks like you are, make sure your book is in series and that you keep your new release price high, priced at least $2.99. You won't sell as many books but you'll still get back a couple hundred dollars.
For me, it's still worth it in advertising a book launch. They used to say spend around $500 in marketing to launch a book... ah, well, here you are. The promo should land you a new release bestseller tag--not guaranteed but more likely than anything else.
Your other option is Written Word Media's New in Books feature. Pretty comparable when you look at it because it's half the price.
If the book isn't in series for co-sales, I'd hesitate. Good luck!