In theory a moderately large meteorite would be very valuable; nickle for example is found in high concentrations, in fact most nickle-iron meteorites are essentially high-grade stainless steel. I would estimate the scrap value of a meteorite to be at least $5000 per ton. Materials with value due to utility rather than rarity, such as nickle, probably would not suffer much of a decline in price even if a large quantity were recovered. Also, metallic meteorites generally land intact except for some erosion. However I think the environmental impact (pardon the pun) would be unmanageable. A meterite of less than 100.000 tons would probably not be economical to recover, and most countries are just not going to accept the risk of someone accidentally dropping an object on them that could destroy a city.