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edited: I've checked other major exchanges, and the prices of listing are just unbelievable. In some cases the price is close to the whole DTC 'market cap' at the moment

I see what you mean.
Novaexchange charges one bitcoin to get listed, and you can pay an extra 0.2 bitcoins a year to keep a low volume coin listed.
https://novaexchange.com/faq/frequently_asked_questions/If it is a new and untested currency we do accept Pay to List service. Currently, there is a setup fee of 1 BTC and a yearly fee of 0.25 BTC - this yearly fee does not apply to coins that have a trading volume of at least 0.2 BTC over a three (3) weeks period. In order to list a coin, its wallet must have an open source code available for inspecting trojans and other malware that could manipulate Novaexchange as a service.
Datacoin market cap = $17,458 USD
Novaexchange listing = $12,942 USD
However Coinexchange.io only wanted 0.25 BTC to list a coin last year. That's a better price if it's still available.
Weve asked coinexchange.io if they would list the coin but they sais
Coinexchange.io said
There is a 0.25 BTC fee for new coin additions. New coins are added within 24 hours of payment.