I've just done some pricing...
300mw 638nm diode with cheapest housing and lens $41 (DTR's Shop)
445nm m140 Dioide with cheapest housing and lens $54 (DTR's Shop)
300mw 532nm Laser Module Direct from China on Ali Express $215 - http://www.aliexpress.com/w/wholesal...er-module.html
Already that takes you to around the total projector costs without factoring in scanners, case, dichros / optics, power supplies, connections, switches, control board, building costs, profit etc. etc.
That should raise a little thought for caution, especially when a Chinese module comes in at $215 on its own at wholesale.
I can't comment on Emma's products directly as I have no knowledge of them. Maybe they're good and they have a very cheap source of parts, but I'd personally I just be a little cautious and check them out properly before purchasing to ensure you're getting what you want, given the price.
Some people on here have bought Goldenstar as a cheaper brand of laser and have been satisfied. Might be worth taking a look at their range and possibly spending a little more.