Ok I will go against the norm here. I have had several cheap fixtures and they are exactly that cheap. Now they both allowed me to keep corals but had to be compensated with additional lights and many upgrades made (start adding hidden costs onto the great price).
The reflectors on the Odyessa and Catalina aquarium stuff are very poor (at best) and bulbs of course junk. An absolute must is positioning away from oversplash as the reflectors/bulb clips/and end caps will rust out in no time. Raising the fixture helps of course but these set ups are already struggling to get light down where you need it so plan on adding two more "bulbs" to make up for it.
I had to replace ballasts in the Odyessa units not too long after purchase but the Catalina aquariums have been fine (work horse ballasts). Overall the Catalina fixtures have held up the worse and had the worst reflector quality and geometry. I still use an upgraded Catalina unit on my 20 long (6 x 24 to make up for poor reflectors) but after 60 bucks of various upgrades and 130 in bulbs..... Reflectors could be replaced but only 4 of any decent reflector will fit in the space as currently the bulbs are jammed in like canned sardines.
I have a TEK Elite and have absolutely no complaints besides I should have bought one in the first place as the money spent on the "budget" fixtures passed the purchase price of the TEK with bulbs.
If you are DIY type the Hellolights kits are a good bang for the buck. When my mother decided she wanted a salt water tank, at 60, she bought a 20 high and has had no issues with keeping corals at all with the Hellolights stuff.
48 Inch 2 x 54w T5 HO Retrofit Kit
So when looking at costs of ebay fixtures you really need to figure.. Actual cost= fixture cost + new bulbs + odd and end replacement parts + amount of corals that you loose trying to see what you can keep + time spent replacing.......