[simik]

4 letters + 6 digits PSK, roughly 39 bits of entropy, about 730 hours to exhaust the search space on a single GTX 970/R9 290X.

EDIT: I'm surprised it costs 1,000 GBP to cloud-hack a PSK of this length, considering there are lots of GPUs mining cryptocurrencies at about $0.15 an hour.

[sp332]

Per hour, the cloud is way more expensive than owning your own hardware.

[hexane360]

I need to get in on this business :P