Moneychangers

GOT up fairly early today and was wandering through Prague old town before many of the shops, including the money exchanges, were open.
A man stopped me in the street and asked: "Are you form Germany?"
I answered: "No, from England, " and he asked if I wanted to change some money.
Now I very much follow the old rule-of-thumb of going on holiday with more than enough clothes but not enough cash, so I was pleased when the man offered me an exchange rate of 29.50 Czech crowns to the pound.
I had got 28 to the pound at Victoria station in London, and the best I had seen in Prague over the previous few days was also 28 to the pound.
When I told the man I wanted to change £100, he tried to get me to change more, but I stuck to £100 and he offered me 3,000 crowns, ie an exchange rate of 30.
By this time I was starting to suspect something was wrong (a brilliant deduction, Sherlock), a feeling reinforced when he looked along the street as he got his money out.
The notes he offered may have been genuine, but I got cold feet and walked on.
Later in the morning I went into a proper exchange shop to inquire about the going rate - none was displayed for pounds - and was offered 23.50.
I declined, and the assistnat, after asking how much I wanted to change (£100 still), said: "I can give you 2,750," ie a rate of 27.50 to the pound.
I shook my head and he asked: "What rate do you want?" I told him I had seen 28 on offer, and he replied: "I can give you 2,800."
We made the transaction and I asked him about the street changer, and he said I was being scammed, and showed me 500-denomination notes of the same design as the street changer had offered.
If I understood correctly, I believe these notes are Hungarian and of very much lesser value than the Czech koruna.
I felt reasonably pleased with myself, although it was not long before I thought: "Maybe I should have asked for 28.50."
But I guess the real moral to the story is that sometimes you do need to look a 'gift horse' in the mouth, even if the person making the offer seems very plausible.