If you didn't spend too much on the case, you could still build a decent 5508 and put an eta movement in there.
Movement- $100-200- either a 2824-2 or a 2846-2- don't know which one will work
dial- say from Yuki- looks like they don't have a 5508 dial right now- might be able to use a 6536 dial and knock off the dial feet- $113
http://www.yukiwatch.com/catalog/item/8677972/9954496.htm
Set of gold submariner hands from Clarks- $15 or so.
Movement ring- #2 rafflestime or Helenarou- $15
a sympathetic watchmaker could put it all together for $50-100- it's worth at least $40!
You'd need a bracelet or a strap- another $20-40, more if you go with a Yuki rivet.
I built a 5508 in 2008 with an NDT case and dial ($1080 or slightly more)
a 1520 movement- $880 plus $200 to service- a 1530 would be correct, but I bought a gold Air King and didn't want to steal the 1530 out of it.
6mm crown- $30-40
Clark gold hands for Rolex 1500 movt.
rivet bracelet that I had
WSO bezel insert- $35 with a decent acrylic pearl
T-16 crystal- $75- can't touch em for that these days!
Watchmaker put it together- under $100, maybe $75
So I have close to $2,500 in it
Sorry for the crappy pic, but you get the idea. I don't really call this a franken because the only Rolex parts are the movement, crown and crystal.