As others have said, don't fixate on how much they are offering on the trade. The only important number is the final transaction price. IMHO the best approach is to separate the transactions. Make your best deal on the new bike. Unless you are in a strong market, dealers should be more than willing to discount a new 2019 CVO. I have no idea what if anything H-D gives them on carryover bikes, but you can figure they have about $8k in gross profit figured into the MSRP before any other Harley incentives.
If you want top dollar for your trade, the only way that is going to happen is if you sell it yourself and happen to get lucky. The market sucks right now in most areas. Otherwise, if you're like me and want nothing to do with selling direct to an individual, your only option is to either sell outright to a dealer (doesn't have to be the one you're buying the new bike from), or do a consignment deal if you have a local dealer that still offers that option. Unfortunately the Harley market is flooded with bikes, new and used, so you really have no leverage when selling your old bike. It sucks, especially for people who still remember the way things were in the 90's, but you have to look at the Harley market these days as being just like the automotive market. Harley's these days, including CVO's, depreciate immediately and rapidly.
Btw, all the money you sank into modifications doesn't count for much either. Some places offer nothing extra for mods, others may allow ten cents on the dollar.
JMHO - Jerry