Bomba, I was concerned about the future upon new coin reward phases out, and transaction fees replace this as an incentive to continue spending computational effort to create new transaction blocks.
Me too, so let's look at this limited information:
http://blockchain.info/charts/transaction-feeshttp://blockchain.info/charts/transaction-fees-usdWhile the miners' cut in token form is rather stable across various Bitcoin valuations, the extra popularity and value of Bitcoin could provide a proportional relationship so the efforts are rewarded correctly.
As seen above, for values of 20 USD/BTC, fees were around 500 USD, for values of 250 USD, fees were around 8000 USD and for values of 60 USD, fees were about 2500 USD. Would this satisfy your concern?