I'm not convinced, I bought a factory refurbished 2555lmt last week from tigerdirect and it only came with a normal TA20 charge cable (unit says LMT on it), traffic has not worked at all for 3 days. Today I swapped the cable for the traffic receiver type GTM 25 from an older garmin of mine and all of a sudden the traffic on the unit started working again. I'm about to send it back to tiger as the cable is $70+ on its own.
Not sure where you're getting the $70 price for the traffic cable as the ones I've seen online are around $20-$30. Either way, I don't think it will be a deal-breaker as I've heard the traffic capability is hit or miss. I'm not really expecting to use it so if it doesn't come with it I'm probably going to keep it anyway.