现在建房子合算吗?

我买了一块lot,是银行的, only $28K/0.5 acre. The most expensive builder in my area said the building cost is about $100/sf including landscaping and upgrading. the standard builder is asking about 480/sf.
in my area, the house price is decreased much from 2009, this year is even worse than last year. Do you think it is good to build a house , or t obuy a built home. We have kept looking for a year, but did not get suitable house. Do you think we can still keep looking, just just build a new one?

Do you think the cost of building home will increase next years because of inflations? the builder said the building materials decrease price now because tehre are too many materials stocked in warehouse, and labour cost is low, builder's profit is low,I doubt his words,,any comments