Well, MDF performs better than ply as it is less resonant, but for touring cabs they are not as sturdy. I wouldn't count on them to hold up for too long. 30oz magnets are nothing to worry about, but only if they are Neodymium. A mud magnet of that weight on a 10" driver smacks of price-driven engineering. At these prices, I can't imagine them using N/D drivers. The 10" N/D driver speced for my horn cab costs $150 alone.
In a nutshell, at this price, you can't expect anything but cheap drivers in MDF cabs. Price 3/4" Baltic Birch lately? They may sound good, and they might be put together right, though. At least they use 3/4" MDF.