No, it's a fair game ... now with 0.12.0 : we can purge mempool from 0-fee transaction automaticly during heavy (and low fees) period of time.
https://bitcoin.org/en/release/v0.12.0
Previous versions of Bitcoin Core had their mempool limited by checking a transaction’s fees against the node’s minimum relay fee. There was no upper bound on the size of the mempool and attackers could send a large number of transactions paying just slighly more than the default minimum relay fee to crash nodes with relatively low RAM. A temporary workaround for previous versions of Bitcoin Core was to raise the default minimum relay fee.
Bitcoin Core 0.12 will have a strict maximum size on the mempool. The default value is 300 MB and can be configured with the -maxmempool parameter. Whenever a transaction would cause the mempool to exceed its maximum size, the transaction that (along with in-mempool descendants) has the lowest total feerate (as a package) will be evicted and the node’s effective minimum relay feerate will be increased to match this feerate plus the initial minimum relay feerate. The initial minimum relay feerate is set to 1000 satoshis per kB.
Bitcoin Core 0.12 also introduces new default policy limits on the length and size of unconfirmed transaction chains that are allowed in the mempool (generally limiting the length of unconfirmed chains to 25 transactions, with a total size of 101 KB). These limits can be overriden using command line arguments; see the extended help (--help -help-debug) for more information.
Cheating don't work anymore ... when Bitcoin network is busy.
are you for real?
Being able to drop customers is technically doable and it was even before of 0.12, the tools at your disposal are more and more effective.
That said, the real problem is that your turning down customers not because you can't handle them but just just because you decided that your product deserve higher prices.
You decided to do it without advertising the price increase in advance.
You decide to do it even if your competitors have better products to offer both in absolute terms and even in relative terms once you discounted your recent price rise.
Sure bitcoin still have the network effect on its side, but not for long.