Do Polish people can afford very expensive cars?
Most of the expensive cars here are not actually owned but instead are leased (mainly due to the better tax benefits of leasing compared to those from owning). There's a Ferrari Enzo in Piaseczno, it's leased.
How about Hummers, wonder how many are there in Poland...
Not sure. I know that there is one in or near Bielsko Biala and I've seen four driving round Warsaw in the last year or so.
No McLaren F1's yet?
Given that there are only 72 street versions in the world and those are worth even more than a Veyron, it's not surprising that there are no F1s in Poland!