Let's do the basic math here. A unit is 3800 EUR. Shipping another 100 EUR (within the EU).

A821 is rated 1200W. Let's have our hypothetical miners collocated. A standard price for collocation of a miner in central europe is around 40 EUR. A standard price per 1kWh is 0.14 EUR. A 1200W device will do 864 kWh in 30 days (a month).

So far that's 120 EUR for electricy and 40 EUR for the collocation. 160 EUR total per unit.

Let's say we get 2 units.
Costs: 160 x 2 = 320 EUR a month.
Profit at current difficulty of 1.93113645449e+12 at 22 TH/s and Bitcoin value of 14900, 1082 EUR a month.
Net profit: 1082 - 320 = 762 EUR a month.

ROI on current prices: 2x 3800 + 100 = 7700 EUR; 7700/762 = 10 months and 3 days. Assuming difficulty does not change.

This make little sense. Judging by how difficulty been rising recently, and how volatile and violent Bitcoin's been for past month, even full ROI is unlikely.

Correct me on anything.

For a small time private miner looking to acquire 1-5 units the most reasonable strategy is: Wait and see what happens on the market.