There's also a question of availability, ASM tubes are only sold in batches of 10, which excludes small home miners right from the start. In USA there are two group buys which can give you an opportunity to buy only a miner or two, but for the rest of the world Bitmain has no alternative, they are the only manufacturer on the market delivering right now. That said, I don't believe buying any equipment including Bitmain's will ever return the BTC invested in them, fact that people are still buying only shows most of their customers recoup some costs by reselling the equipment or having access to unpaid electricity.