Hi! I don't have experience in your field, but I just wanted to say congrats for the idea, and for your business in general: it sounds like you're doing good!

It sounds like you have two problems to overcome: money and the actual shop.

Money-wise, if you think 6k/month would cover salary, rent, utilities and other expenses, then you're already winning: like you said, you'd provide a better service to your customers, and that is very valuable on its own. Not to mention opening another line of business, which helps long-term.

Of course, you should factor in the initial investment in static assets; but I expect asset turnover to be quite good for you: you'll be able to maintain a steady flow of orders, so you're safe in assuming that your initial investment in lasers, etc will pay off.

So, all that remains is to find a good jeweller, right?

Sorry for my rant :) and best of luck!
Vlad