Help with difficult client

so i agreed to make a flash site for a friend of mines small company he was working with. my first mistake i know. they already had a flash site up but it really sucked and customers were complaining about it so he asked he to help. he told me they didnt have much money so i said id give them a really good price, $300. it turned out being a huge pain in the a#@ working with them and to top it off it was a real hassle to get them to pay the $300 for the site when it was finished.
so now months later ive been getting emails from them asking for the flas for the site. i already explained to them that it doesnt work like that the flas belong to me if they want changes to the fla theyre going to have to pay me for it. but they continue to push for the flas. im tempted to just give it to them and forget about it, but i just cant, i spent way too much time working on it and theyve been such jerks to work with. not to mention the reallly fair price i gave them for the swfs. anyway my question is am i right about this? they dont have rights to the flas do they? if i were going to sell them the flas what would be a fair price? i forgot to mention that i redesigned their logo also which i included with the site, really bad move on my part, but i was trying to help a friend. any advice would be very appreciated!