....have a '94 E500 w/ 42k miles:
In June of this year I did an enthusiastic CannonBall Run/ Ralley from N Cal to S Cal where ambient temps were consistently a tad over 100 degrees (Ca Central Valley dry heat). Result: a stimulating troublefree 1400 miles over 3 days w/ triple digit speeds the norm.

Later that June (this year) I did another trouble-free trip to Sacramento,CA where ambient temps were 110+ degrees in stop and go traffic/ a/c on- - again no problemo. ...again dry heat condition

Seems like the 500e/e500 owners are a 'best of all worlds' type of group- that would like the engine temps to ride in the 90 degree range +/- a few degrees for all the right reasons...

although not as desireable- - on the other side of the coin, I've not heard of the higher overall operating temps of a 500e/e500 be the demise or proverbial nail in the coffin (longevity/ operating shortcome) for such a vehicle ...and have not heard of any 500e/e500 overheating due to an inadequately designed/ inadequately engineered cooling system (as yet- ...knock on wood)

As a matter of good habit though, being an enthusiast, I regularly pop the hood on the E500 to allow as much engine compartment heat (which is significant) to escape as quickly as possible (vs. linger). My feeling is that if the car is operating according to way the Porsche and MB engineers intended....higher external ambient temps (100-110 degrees) w/ not be a significant hardship in its ownership (we have Texas 500e/e500 owners and owners that regularly track their cars that will probably offer their valued opinions and experience as well).

RE: pricing: I think KBB/ Edmunds continue to apply a general depreciation & wear and tear math formula to their figures and generally that appears to be OK. At times, the true market of a specialized vehicle will not follow the canned formula and start to break out on its own- - I imagine, in time, KBB/ Edmunds/ CPI/ Insurance Tables w/ follow to become more accurate to actual market sales pricing to estimate value.

If you can acquire a nice example 500e/e500 at or below book- - you've can congrat yourself on a steal....there apepars to be more well used 500e's available for sale out there (vs. not). I've observed real (USA-wide) selling prices for low-mileage examples landing consistently in this range:
>92-93's: $26-$35k
>94's: $32k-$48K

Also market values appear to be stabilizing for the 500e (vs. significantly falling further) for the creme of the crop vehicles. Naturally one can purchase a 500e for as low as $15k-16k and an E500 in the $20k's....depends on what standard/condition vehicle you desire to own.

Good luck and let us know what turns out. You may need to search USA wide and be willing to travel to get a primo example....
Auto trader has a '94 E500 with like 45k miles Starmark warranty w/ 18's and Pilot Sports @ $48k + tax + lisc (addl 2 yr Starmark @ $1500)....fyi- I've referred no fewer than 6 people to that dealership and they will not sell it for less than full pop $48k + incidentials!

Tom- maybe on to something re: a lack of volume in determining accurate KBB/ Edmundsm, etc. market values .....as there are only about 1500 NA version 500e/e500's in the US. In either case, there will always be a significant range in vehicle values based upon condition, history, maintence, and mileage- specialty vehicle or not.

RE: C36/C42:
different animals vs. the W124 5.0L, but generally High Perf vehicles share the same trade-offs (perf model v. standard model).

good luck and let us know what turns out for ya
-fad