As I mentioned in another post:
Not everyone goes by the market rates, or by the standard fare provided by the hotels. I know, with absolute certainty, that I'll be incurring a huge loss based on the dinner banquet alone (not considering photography - $6k, bridal gowns/accessories/shoes - $12k, flowers - $800, band - $2k, MUA - $1100, extra decor - $100, flower girl/pageboy outfits - $200, etc), so you'd need to take those into consideration too. My tables are about $1800 each (10 pax), and I definitely don't expect any guest to give $180 each!!
I agree with most here though, that people should RSVP early to inform the couple if they're unable to attend. It's absolutely rude to simply not turn up, or send a SMS an hour prior to inform of your non-attendance, the hotel charges per table regardless if there's only 4 people seated, plus I'll have to add $120 for every Halal and Vegetarian menu ON TOP of the per table pricing. Sigh. Imagine a table with 4 Vegans in a family (hence the need to seat them together), and forking out $2280 for that table! Everything is so ridiculously expensive nowadays, and my husband and I are finding ourselves in a huge credit card debt. Sigh. And I thought that was supposed to be a joyous event, yet it's so bogged down with monetary considerations, like the OP's post!