Damn, in Vitello Bleu and Hidro Oceano?
Sounds damn sick.
You need to meet them to take measurements, I believe.
They usually send the actual shoe before the finished stages for you to try on. Give feedback and send back, and they make minor adjustments.
At least this is how I have seen it done through Bonafe.
That price depends on where you go, I guess. As a retailer though, you do have costs of shipping back and forth, as well as the cost of the bespoke last to take care of.
Don't have any experience with Meccariello or the service there.
Edit: and to be honest, I think a modified last fully finished with machine made goodyear for 300€ is too cheap, but if he sells directly to customers, I'm sure it's possible.
Modifying lasts is easy if there are few and simple modifications, like added space over little toe or adjustment for high instep. If these small adjustments get many, or more difficult adjustments (say flat feet), then it's a big risk for the retailer too. Arranging for a modified last is a great service and lots of work, and should definitely not be a charity case. That sounds like asking a bespoke shoemaker to create your last for free, as they are guaranteed to get multiple orders in the future. However, they have no such guarantee.
Anyway, good luck on your Enzo project. They make beautiful shoes at a beautiful price! :)
The classic Jordan dunk over Mount Mutombo with the finger wag is still etched deeply in my mind. Lol.
Nice boots, by the way.