The above sprayer is
available here for £99.
Can't comment on this model but the pump on the one I bought from the ebay shop lasted about 3 months. I got a replacement for around £10 and fitted it easily but then the battery wouldn't charge so I dumped it and went back to my gloria sprayer.
The problem is that if you want reliability then you have to pay around £200-400. A lot of window cleaners swear by the
FaceLift BigBOY Backpack at around £180 and have received great backup when things go wrong. There is also the Gardiner backpack at around £108. Or you could look at the Ashbys offering at around £480. Then look at agricultural sprayers from birchmeier that start at £600.
The cheap ones on ebay are about the same build standard either the pump fails, the battery dies or the hose splits and leaks. They also don't have viton seals and don't much like very hot water. When you consider their wholesale cost is around $40 from alibaba you can judge for yourself how durable they will be.