For now and for small gains. It's gonna be different in the future in my opinion.
What are the gains on a $100 GPU? Mining was never intended to be a high profit, free moniez for everyone system. The purpose of mining is to protect the network and miners are paid a fee for that service. Mining is an almost perfect commodity and as such overtime the margins are going to be very low, especially as the risk premium declines.
Still the reality is you CAN get into ASIC mining. Maybe you don't like the return but that doesn't change the fact that you can get into it.
The eruptor uses 2.5W of power so once bought while your revenue may decline it is unlikely it will ever be unprofitable. Difficulty will be constrained by electrical efficiency and that will ensure those eruptors will be able to trickle in some revenue for a long time.
Didn't say mining is a get rich quick sheme, I see it more like an investement.
But the guy who'll pay 50000$ for 1000gh/s for example will not be comparable to a guy who'll put 100$ for a lot less hashing power and wait a long time to even break even on the hardware. When bitcoin gets taken even more seriously then now and more and more people start to mine a lot of rich people will invest into mining and be able to buy the most gh/s.
The reality is most people mine for the money/bitcoins not to help keep the network secure, that's just a side thing. But I'm really just trying to say that ASIC is not a significant improvement for bitcoins in my opinion. People will have to pay more and more for them to be able to mine with a gain and the network won't be significantly more secure by that.