Class 800 Azuma

The $10 price is what I saw posted by a guy in the USA and is to cover the cost of the decoder only.  Here in the UK you can get a pack of 6 sets of car lighting for around £45 if you shop around for them.  That would be enough lights for 6 passenger cars and these will work without the decoder, the only issue is you don't get the option to turn the lights off remotely like you would if you have decoders, but as you would need 6 decoders as well its just not justifiable in my opinion.  Besides if the real world trains are the same in other countries as here in the UK they always have the internal lights on anyway regardless of whether it is day or night outside mainly because they have tinted windows these days.  So having them on permanently isn't an issue in my view.  So assuming I only add lights if I can do 6 for £45 that would work out to around $60 I think at the current exchange rate, so yes $10 a car for lighting

If you are prepared to buy them from Japan you can actually get them even cheaper, the only downside is shipping and VAT when they land here which will make them at least as expensive as the locally sourced ones.