Is It Real And How Much Should I Have Paid Roman?

It looks fine to me. The lettering is a bit rough and disappears in a couple of places, but I've seen worse on coins of this period. The weight is at the upper limit for the denomination at the time. The very rough, jagged edges are also typical of the period.

Further info on your coin: the obverse inscription would read (if you could read it all) M ANTONINVS AVG TR P XXIIII - the 24th year that Marcus Aurelius received the tribunician power, or 170 AD - a fairly precise date for a Roman coin. The reverse type is SALVTI AVG COS III, Salus (goddess of health) feeding a serpent on an altar. Similar to this example on Wildwinds.

Nice coin.

Yes, the denarius was still relatively pure silver at the time (about .800 fine) though whatever the alloying agent was, it seems to have made the metal more brittle if the cracking often seen on denarii such as we see on this one is any indication.

As a general rule, if an ancient coin "looks silvery" then it most likely is actually made of silver, or at least debased silver. They hadn't discovered nickel or any of the other silver-coloured metals that are used in modern times to imitate silver. A notable exception are some coins from ancient India, where a source of copper ore naturally high in nickel produced some very silvery-looking base-metal coins, a fortuitous accident the ancient Indians made full use of.