We are doing this for most of our start up pools.   For our first pool (wdc.cryptotroll.com), we gave away 100% of our fees to top 10 block finders, plus additional 10% of all donations to the winner.   This is significantly less.   The idea behind this promotion is to attract miners to join our pool.   We would be happy to receive 70% of future fees, instead of 0%, if pool is not adopted by miners.  It is not very complicated.

PS: Thank you for thinking that our promotion is so great it must be a scam

CryptoTroll