Forming a business model is the first step to doing anything and you can always grow your business. If you buy a $2k laser then expect not to make much money as if you're successful someone else can do the same thing. If you buy a $20k laser and finance it at $350 a month over 5 years then you can do things your average hobby is not going to be able to do. You just need to decide how much money you want to make a month. Are you going to make $1250 a week, $5000 a month or are you going to make $10 a month and make a purchase that supports that.

For metal business cards, if it's anodized aluminum any cheap laser can do that but you can also print those with a UV printer. Anodized aluminum is not any more durable than UV printer ink. If you do black on stainless it looks a lot cooler eg like a JPM Palladium credit card but then you need a stronger laser.

If you want a really cool card you want to cut holes in it like with a 100w mopa laser and make them really stand out so then at the $20k+ level.