(spoiler: kind of a loaded question, but feel free to play along)
As of 2015 we can still obtain EM's from free to a few hundred dollars for your basic Craigslist beater with decent but peeling/red-faded backglass, good playfield with some wear, faded cabinet art with some scratches, and "mostly working" in need of a complete shop job condition...
...but what about complete, minty, better-than-new restorations? As far as I know, no one is tracking this. Let's do a little math...
Dave currently owns an EM which has been sitting at the back of his garage for years. He wants it taken to "better than new" condition. Assuming he doesn't do any of the work himself, he orders...
1) A comprehensive 30-hour shop job in which every mech, switch, lamp socket, contact, lever, score reel, stepper, relay, button, spinner, drop target, slingshot, pop bumper, flipper, motor, electrical connection, and jones plug gets disassembled, cleaned, re-soldered, replaced, adjusted, gapped, sprung, tightened, fixed, burnished, lubricated, re-riveted, and/or replaced. I know of at least one shop in Texas which charges a minimum of $750 to do this. Even then, not "obsessively"... but let's assume so for this example.
2) A nice NOS backglass or quality reproduction, new playfield glass, and set of playfield plastics. Let's use $400.
3) A cabinet repaint (disassemble, stencil, strip, sand, bondo, prime, match colors, paint, apply webbing, paint, reassemble). One of our local members is well-known for his quality work in this regard. Typically $500-$600. Let's use $550.
4) Polish, rechrome, and/or replace all external metal parts (coin door, plate, strike plate, legs, rails, buttons, shooter). Let's use $200.
5) Clear coat playfield (strip, prep, fill inserts, touchups, clear, repeat many times). Let's use $500... somewhere between HSA and DIY for a good candidate.
6) Reassemble and test. Did we miss anything?
Shop rebuild: $750
Glass & plastics: $400
Repaint: $550
Metals: $200
PF resto: $500
Total: $2400
At this point we still haven't discussed the "better than new" tweaks. What about installing cabaret lighting under the ball arch, as Gottlieb did for many years? What about stealth LED's? What about double lighting star rollovers? Maybe replace all lamp sockets including custom rebuilds of lamp socket strips and those pain-in-the-ass Bally backbox sockets? If we include all that, let's add another $300... minimum.
At this point, Dave has spent $2700 for an outstanding bulletproofed museum piece. He'd have to sell it for $3000 just to break even if you also count the "base" value for the original game as-is ($300).
Is this too much? Or not enough? Or right on?