Rollback between castles during auctions.

Ah, if only someone would share such information... I understand that this is quite subjective, but it would still be quite useful.

I don't have any, but someone definitely does. Here's a good example.
Gomunguls vs HellLighT, JC, SoD, and a pair of Inferno/Tower maps are up for grabs. The players negotiate until they reach 5800 (or so), and Vitaly buys the Tower, which shocks many (including me).
For comparison, AmiLu and I negotiated for an Inferno map during a CIS tournament in St. Petersburg, and we ended up paying around three thousand. How can you talk about tables after that? :D