Greetings redux, Postmaster!
As Amy already pointed out, these building are to last a millenium! So when you divide their cost by their lifespan, they're really quite a bargain.
Further, the Baha'i temples (currently seven with an eighth currently under construction) are our gifts to the rest of the world: no specifically Baha'i activities are held in them. (For example, a Baha'i can't get married in one.)
And a point to bear in mind is that we're taking great pains, at our sole expense, to design and build the most perfect places possible! (If you read any of the reviews about our temples and world center, I hope this will become obvious.) I humbly suggest to you that most religionists of any faith would very likely endeavor to do the same sort of thing. None of this is "iconry," please note--just beauty for the love and worship of God.
Nor has this hampered our development projects, which again are funded solely by us and of which there are well over a thousand around the world! And these benefit society at large, not the Baha'is. (They're things like irrigation projects, schools, and disease-eradication measures. Screwworm investation was completely wiped out of NE Africa through the efforts of the Baha'i development program there, for example.)
I would also humbly suggest that others really aren't in a position to dicatate too much how our money is to be spent given that it's 100% our own money, voluntariliy contributed, and that we neither solicit nor accept funds from anyone else.
One quibble for a third party, BTW: the Wilmette temple is in fact the second one ever built. The first was in Ishqabad, and was confiscated by the Soviet government (later an earthquake destroyed it).
Many regards,
Bruce