You did very well getting those components at those prices. If I could match your experience I would go for it.
The Mezzo I-4 has a 44 tooth four bolt chainwheel. In all my googling I couldn't find a 53 tooth four bolt chainring, hence my thinking of need for new crank. The Mezzo D-9, and D-10 already come with 53, and 56t rings and 5 bolt.
I got one price for wheel built with I-motion 9 hub 696 GBP (398USD) plus shipping then add cost of shifter, chain, cranks, misc., I would be close to, or over the 619USD (990GBP) that I paid for the Dahon Mu P24.

By the way, the price of a new Mezzo D-9 in NY is just about double what you paid for yours.