That's the price for the plastic fantastics. I had a heft of one of the club handled metal shorties recently, which does feel pretty robust. At 1.8kg though, it's not something I'd want to hold up in my sight line for long:
http://www.taiwangun.com/en/springs-2/cm-357m-full-metal-black-cyma?from=listing&campaign-id=19
I have a pistol handled ASG tri shot, and yes, I'd call it tiring using one. The significant part is that you need to complete the action in one motion. 99% of the way there isn't good enough. If you fail to complete the pump, you risk double feeding, or in my case I lost my grip, the pump shot forwards and wrecked the mechanism at the front of the slide. It wouldn't slide quite fully forwards again and somewhat bizarrely that stopped the trigger from operating. I mention this because I only just figured it out and got it sorted this weekend by hacksawing parts off of it until it pewed again.
So I would agree with getting one with a solid or sliding stock rather than the pistol or Mad Max stylee ones, and have a backup to switch to later in the day when the will is there but the flesh is weak.
On accuracy and range, never mind .28g, I'd say mine under-hops 0.2g and needs to be used ballistically. With a fixed hop (well, three of them) you're at the mercy of whatever random rubber or tension they put into that specific gun on the day it came out of the sweatshop. You might get lucky, you might not.
That all sounds pretty negative, but they're actually great fun to use, in large part
because of the physical effort required. I'm glad I've got mine sorted (and of course, despite what I just said about stocks, I've just fettled up a wooden club handle for it

) but I wouldn't spend more than £40 on a plastic fantastic. I doubt that the internals in the metal shells are any more robust.