I think I pretty much stand close to my first post. I was the first one who said it is close to a fair trade.
Now I am talking used value, and usually the higher the cost of a bass (and esp if it's custom) the bigger percentage hit you will take on the new price, even if it is still mint. Moduli have notoriously low resale value (not because they are bad, but because they are priced a bit high new and they are fairly common.) The $3600 modulus would still be under $2k used... let's say $1900. The VJ I previously put optimistically at $1200... You can see these occasionally one ebay for the mid 900s but they usually go over 1000 (not by much and if so not often) so lets say $1100 fo the vj. Still it works out to about $3000 for both.
Is the drozd worth $3k. Well if it is selling new for $5k what is the resale value? Remember you take a big hit the higher the price but there are other factors too. If he is not making them fast enough to keep up with demand then they will have higher resale value (Rick is a good example, so is Wal.) Also some very established premiere builders get high resale value (think MTD and Sadowsky.) Some mass producers of incredibly good instruments have very poor resale value (Peavey Cirrus is an INCREDIBLE bass that loses alot of value if not new, not because it is bad but because it is easily obtained... same with certain warwicks and G&Ls.) Normal basses in the $1000-$3000 range are worth roughly half on the used market (think Pedulla, Spector etc.) Some established patriarchal brands hover around 55-60% (musicman, fender) Where does drozd fit? Well take half of $5000 and start from their... $2500 plus or minus $500 (probably not minus in this case...) OK so I'd say the drozd is worth in the upper $2000s on the used market. Lets say $2800. So $3000 vs $2800. It is pretty close! (Disclaimer: I don't know enough about the demand for drozd so it very well could be worth more than 3k used.)
Now the above applies to private traders, not stores (usually anyways.)
If this is a store willing to do the trade consider yourself lucky. A store would not give you 100% of the used value on the modulus even if they can flip it quickly. I don't think most stores are as bad as this but GC would give you about $900 trade in on the Q6 and about $500 on the VJ if you are lucky. I think there are other stores that will give you 60-80% (of used value) and maybe more if you are getting store credit, but I know a little less about percentages for stores than I do about percentages on the used market. But if you know the store you are looking to trade into, just get an idea of what they would offer for different basses (there may be a diference in trade in value and value if they outright buy it from you so ask them about it.)