Vortex sprayliner would fix your issue. I did a carport last year that had a room under it for protection. Also put it in our firehall with cracked concrete that leaked water into lower levels. Works great when a little flexabilaty is needed. Any color you want, any thickness you want.
Its also important to mix your thinset exactly. Too many people mix it wetter than it should be for ease of use but it makes the thinset weak bonding. Make sure you get good transfer on the back of the tile when setting, lift a set tile to see if it has suction. If the thinset is too dry it...
We have insurances to pay and licensing, truck etc. Its hard to make it at $5 sf. with all the costs involved. I could sell everything and work at walmart and probably make more.