Even though they cost more than watchs built from rep parts, frankens are a much better deal--the effort is the same and you will end up with a watch that easily passes as gen 99% of the time at 1/3 the very cheapest you can get a used gen.
To build a franken I would reccomend:
A good handwind case and xtal either from ebay or the trading area-$100-$200
A good crown guard, which should be modded in the standard ways. If you can find one, I am partial to the Cg's found on the cartel's "Ultimates" (88,63 etc) which you can often find in the trading area as folks upgrade to jimmyfus and gens. $30-60
Gen 113/111/112/ dial (the dial makes far and away the biggest difference. In fact, IMO if you're not going to use a gen dial, you might as well save the money and just wear a stock rep since the flaws on the rep dial will be noticed long before any other rep-part flaws. $400-600.
Rep hands to match dial $75
Accurate solid caseback $25-100
T48 crown, or if you are a stickler for 1:1 functionality rather than appearance only, a gen. $25-200
AR removed ot added (chief single sided) as the watch requires (a-c series PAMs=no AR/all later PAMS single sided AR) free-$45
A Gen strap is the easiest way to improve a rep or franken $75 and up.
Lume notwithstanding, labor from a competent smith should cost no more than $100, probably less.