SEDO appraisal is based on fictional values and not real values
do yourself a test,
try to add names in really useless extensions but with high valued keywords.(NOTE: add as in, reach the screen where SEDO values the domain just to see the appraisal, do not go further)
In reality almost no-one would buy any keyword in those obscure extensions but SEDO would value it at the 10k range because it bases the appraisals on extensions like .com /.net ,etc.
The same happens -as very correctly @dotbay mentioned- for domains that have real high value. SEDO will tone them down -again- based on some weird internal valuation system of the past
just ignore automatic appraisals. Buy domains when you know your target audience and have a good idea what they'll probably want to spend for the name.