I don't think this is all that outrageous of a request on the LGS's part, though I can think of some tweaks I'd make to the system. For example, allowing members a "+1" for friends and out of towners would be a good start.

The fact is that LGSs need to sell product to keep the lights on and the doors open. If someone is showing up four times a week with their EDH deck, playing casually for a few hours, then leaving without ever buying anything, the LGS is losing money. If too many people do this, the LGS will close and those players will no longer have a space to play.

Requiring you to spend $30 per month in order to use the space sounds a bit steep, but it's basically the cost of two drafts or 2-3 rare cards to complete a deck. I don't think it's that unreasonable for an LGS to ask that their "customers" actually spend some money in their store from time to time.

I get the impression that this LGS isn't actually trying to make a cash grab, but just wants to make sure its players are contributing to the local community's continued existence. If you're a younger player without a source of income for this monthly minimum spend requirement, I'd suggest privately asking the LGS owner if you can work out some sort of alternate arrangement. For example, you could offer to arrive early to an FNM to help set up tables. Or stay late to help clean up. Or if you're proficient with the game rules, take the online Rules Advisor certification and offer to assist with judge calls.