Payment in Euro's vs Zloty in Poland... Does it sound like a rip-off?

I recently asked if I could pay for a two week intensive language course in Zloty's because the exchange rate between the Pound and Euro is very weak. I was told I could pay in Zloty or USD.
When I asked for the price list in Zloty I was told they simply use the Euro price and work out the Zloty price by that days exchange rates.

Does this sound normal?

If someone wished to purchase something from me, in the UK. in Pounds Sterling I would not have to check the exchange rate to see how much of my own currency I wanted!

Is this common procedure for Poland or does it all sound like a bit of a rip off?

It's a normal procedure not only in Poland when a price is fixed in one currency with the possibility to pay in other currencies as well. It's done that way for banking and tax reasons.
Even if you have price lists in different currencies there's always the small print stating prices in which currency are fixed and in which currencies are subject to change.
It looks like Euro is simply the basic currency in the case you described, hence any other payments (PLN or USD) are converted on a daily basis (they should use NBP - National Bank of Poland - exchange rates).
And how could it be a rip off, when they are getting less money in Polish zloty from it? (A year ago it would be 3.80-3.90 PLN for 1 Euro, now all they can get is 3.40 PLN)

thanks, Krzysztof.
I assumed the Euro was increasingly strong against the Zloty (as it has been against the USD and GBP). It is only after your post I checked the recent history of the exchange and found the opposite is true.
This has changed my view of the language school completely.
Cheers.