ParanoidObsessive posted... yes?
It doesn't really matter whether or not the coins are stolen. You still need to find a buyer who actually appreciates the appraised value of the coins and is willing to pay that amount. The average person can't just walk into their local cash-for-gold dealer or pawn shop and have the person behind the counter pull out a copy of Numismatics Monthly and offer you $30k for them. You need to go through specialist dealers.
High-end collector value items in general are hard as fuck to sell. Because you generally have to go through tons of channels that the average person doesn't really have access to and won't necessarily know how to get in touch with. Which is why appraised value for "collectors' items" can be misleading as hell - you may never be able to get that much for them if you can't find a buyer.
I can own a pristine mint condition copy of Action Comics #1, but unless I can find someone who is actually aware of what it tends to go for and is willing to pay that much, it's not much more than pretty toilet paper. The more expensive the item, the harder it becomes to sell.
So yes, for a criminal looking for a quick buck, it's still generally more efficient to just sell off for a minimal amount than to try and full collector value. Because you're at least getting some money out of it, which is more than you had when you started. Rather than going to the trouble of trying to get in touch with specialist dealers, which can actually increase the odds that you'll eventually be pegged for the initial theft.
Even if you have a proper fence you will be lucky to get 50% the value of the coins in general. I assume the 30k estimate is the retail price like if you walked into a coin shop and wanted to buy those coins.