I'd be curious if TRE were to chime in. At one time (a few years ago) the claimed a "basic" backdate (exterior) with color change could be done for $10k. So if you could get a mechanically sound 911 for under $20k (I did this summer), you could do it. But like others have said, the details (i.e. the "slippery slope") can quickly push it over.
I can think of a few on this forum who did their own budget backdates and their cars turned out pretty nice. So it can be done.
..at least that's what I keep telling myself because I want to do the same! 
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Doug
Currently Between Porsches
PART OF MY SOUL: '09 Boxster 2.9 PDK, '86 911, '76 912E, '06 Cayman S, '90 911 C4, '74 911, '78 911 Targa, '01 Boxster, '70 911T, '99 Boxster (#2), '72 911T, '88 911, '99 Boxster (#1), '84 911 Turbo Look, '73 911 Targa, '88 944
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