Happy New Year to you and everyone too...

Aa a rough guide about 25 Euro's in singles, falling to below about 18 Euro's at 100 pcs, and about 10 Euro's at 1000 pcs.

Yes of course, you can't beat the few cents a DS1820 costs, but then it's not a bare chip, but a fully enclosed product with attached leads and connectors, post sensor processor, integral noise immunity, etc etc with integral seals all ready to bolt straight into your pipework or manifold.

If you want cheap, then just use an NTC Thermistor and plot it's curve into a PIC. You can easilly get better than 0.1C accuracy through simple interpolation across 90% of the curve. It's the way it's done in 99.9% of the cheaper Industrial and domestic Controls. I really don't see the point of DS1820's, LM35's etc, they're a waste of money for something that can be done so much simpler if only folks stopped and thought about the problem. OK, if you've only got a single I/O and a dozen items on the interconnecting bus, then fine, but otherwise why?