i like the concept! , i'd start memberships at $ 24.95 U.S.D , Anything less and as you said surfers will think there is something wrong with it! ( keep in mind that your media is "exclusive" unlike the massive archives others have that share the same media. )
i'd skip "trial-memberships" altogether since most surfers can pretty much "download" everything within 2 days for the bargain basement price of $ 4.95 U.S.D
just my spin!

sincerely ~ ..."it's not the "quantity" but "quality" that counts!"...