I actually bought a DT I #71 for $1500 (a high price at the time, though not now)...then Mik at Grant Books had #71 of DT III and IV as well as Desperation for $1800...THEN I've since stumbled on Christine, Danse Macarbe, Night Visions, Dark Dreamers #71...and all the various editions I've been able to get at issue price, for a total of about 21 all with #71.
Other than the prices I mentioned, I have to say that I've been lucky to never have to pay significantly above market price for many of them...but, other than recent limiteds that I got at issue price, I haven't really gotten bargains either.
I am still missing DT 2 -DOTT #71, but I do have the $56 Author's Edition as a placeholder...
I even had two of three Plants with the same number, but I had to let them go...oh well...