With Premium SMS in CZ you can pay only these amounts:
16,18,25,29,39,49,50,69,75,99,100 CZK

The order price is rounded up so it can be paid this way.

With an SMS price of 189 CZK you can, for example, have VIP for 100 CZK and 2x VIP for 20 CZK.

If you choose only VIP for 100 CZK, the price will still be 189 CZK because there is no SMS tier between 100 and 189 (operator fee).

For euros there are many more tiers (by 10 cents), so you do not have to deal with this, but the operator fee is higher.