Edit: I am going to try to start some of this discussion in http://forums.leaflabs.com/topic.php?id=1368
because I think we are discussing stuff where this thread title is not a good fit.
do you think the addon ethernet/usb host as bad idea?
I don't think it is automatically a bad idea, but until I see how an ethernet or USB Host add-on board is fitted, I wouldn't like to give a definitive answer.
An ethernet daughterboard might get in the way of other daughterboards. In that case it was inferior to on-board ethernet.
It might be sensitive to noise, or generate enough noise that it isn't practical to use other daughterboards. In that case their is no benefit to having it on a daughterboard except a lower price to people who don't want it!
In general, I don't like high-speed interfaces (I am hoping Ethernet will be 100Mbits, or USB, 480Mbits) running through header pins without ground. If the board is Arduino header pins compatible, the Ethernet/USB Host board connecter isn't Arduino compatible, so the board should be outside on an Arduino daughterboard footprint. If it interferes with the Arduino footprint, preventing normal Arduino 'shields' being used, then there was little point making the board Arduino footprint compatible (I have no problem with that, if I can make daughterboards on a 0.1" pitch, but some folks may want an Arduino footprint).
So, if Ethernet/USB Host is outside the Arduino daughterboard footprint, there is the problem of making that connection robust. The simple solution is to make the MCU board so big that the daughterboard is within its footprint. In that case, it might be as well have routed the MCU board for Ethernet/USB Host, and have a reduced cost version without the parts fitted.
siy - sorry, I wasn't clear. I interpreted olimexno's cost as the retail price increase of $6 on the board, and your costs were based on part cost were about $5.50. I think quantity is hard to guess. I'd start by assuming 1000-off, where some of the parts are about 50% cheaper (e.g. at Farnell), but vary by quite a large margin.
I absolutely agree, it is well worth considering a high-speed interface. Several people have posted on this forum about projects which need a lot more throughput than Maple's USB. STM32F4 has a theoretical ADC bandwidth of 7.2M 12bit samples/second, which is way beyond full-speed USB.
Something 10x faster than an Arduino is a different machine for a potentially different market, and folks shouldn't extrapolate from Arduino. IMHO Ethernet might be a distinctly different market from USB.
(Edit: can we get this discussion off this thread? I think it is an inappropriate title)