I have this ancient coin from 244-249 AD and I was wondering what it was worth. I got it appraised an I was told it was worth only $5.00 because of its concaveness. Was this guy telling the truth? P.S: this is what it looks like:

Dealer buy of $5 would not be unreasonable given a "sell" value of $15 or so. I note that it appears that besides being cupped, the obverse appears to have several scratches, further devaluing the coin

Without damage, it appears to be a $25 to $50 item.
http://www.wildwinds.com/coins/sear/s2632.html

Damaged, of course, it is worth much less.
Apparently, there is no shortage of these.

As is often the case the true value of the coin is in the history. Little is known about Marcia Otacilia Severa beyond her being the wife of Philip the Arab. This Roman emperor appears on some banknotes of Syria. (Look him up by his real name, Marcus Julius Philippus, as well as by Philip the Arab.) Oticilia might have been killed when Philip was defeated at Verona. On the other hand, she might have died some months earlier, according to the accepted dating of her coins, which end in 248 AD.

I could not place her in the Severan Dynasty, despite her name. Her father clearly belonged to the gens (or "clan") but it is not clear how related they were to the famous emperor Septimus Severus.