A WebmasterWorld thread named Yahoo Search Marketing Account Rep - U Got One? asks what it takes on a financial level, to earn the luxury of having a dedicated Yahoo! Search Marketing representative for your accounts. AtBatt explains there are different tiers to the program, including;
4 tiers of service based on spend.
Normal <$1000 a month
Gold >$1000 a month <$5000
Platinum >$5000 a month <$10000
Diamond >$10000 a month with National Brand Recognition
AtBatt, who says he used to be a Yahoo rep, explains that "in order to retain a dedicated advertising rep, you must quality for their Platinum tier of service." That equates to at least $60,000 per year spend with YSM.
Forum discussion at WebmasterWorld.
Update: I knew it couldn't be that simple, a Yahoo! representative responded to the thread saying;
Hi All, For an accurate, up to date break down of account service, please visit this link from YSM's Resource Center:
But to be clear, our team is dedicated to providing the best service possible to all of its advertisers and publishers. If you have any direct questions around this subject, feel free to send me an email. Thanks
The link provided by YahooSarah, has the correct information.