If you click the selection correctly, it’s not cheap anymore
That’s £5420 in my local currency - still very cheap for a 100 Watt Mopa.
The one’s I’m looking at are on AliExpress, There is a lot less faffing about on there than Alibaba. I’ve done Alibaba RFQs to buy dye sublimation blanks before and I have seen fibre lasers on there advertised for similar prices to AliExpress. I think if (when) I do pull the trigger on this I might go the Alibaba route to see what the difference is in price… I echo all of your comments when dealing with sellers on Alibaba. I too was requested to move the chat to whatsapp and payment off of Alibaba but elected to keep everything there. In the end our transactions have gone smoothly, though I still find it a little creepy when sellers address me as ‘Dear’ 
Cheers,
Troy