You didn't simply pull out of a purchase as far as I can see -- you defaulted on a contract. In the same way that the seller would be liable if he or she defaulted, you are of course also liable.
It is called a contract because it is a contract, simple as that. I don't think anyone should be blaming the legal system in Hungary, which is very fair and open in my experience. Describing this as a penalty is not strictly accurate, to be fair.
I am aware of at least two Irish agencies that have bent over backwards to facilitate people who wanted to change their minds and default; I know of at least ten instances where the agencies in question managed to resell the properties and did not charge a commission to the defaulting buyer. I am also aware that at least one agency has now stopped doing this as a matter of policy, as they were getting p***ed off by amateur investors who didn't know what they wanted and who bent like straws in every wind.
If you bought through an Irish agency you might be able to ask them to try to lay off your property, but they have no obligation to do so. If you bought through a Hungarian outfit, they are generally much more hardnosed and are unlikely to have much sympathy for you.
The reality is that the contract was designed to protect you and the seller; in this case you are the defaulting party.
Why not just buy the property? Try to renegotiate a bit on the price, the seller might prefer that to a long drawn out legal battle. A lot of property in the right areas in Budapest makes for a good long term investment, now that the government is getting to grips with the economy and seems to be setting the groundwork for a more stable economic future.
Depends of course on what you paid for the property too!