Where can I get information about the TODAY'S economic model of the project, and especially - what is the economic benefit from launching and supporting the nodes ?
There was a reward program for those who run full ARDOR/NXT nodes :
https://www.jelurida.com/news/ardor-and-nxt-node-rewards-are-here That program was designed to run for 6 months starting from April 1st. Probably it is over at this point but I think you can communicate with Jelurida support and ask them directly about that.
Jelurida wrote at Sep 30 : "We are happy to announce that our successful #Ardor & #Nxt node rewards program will continue at least until the end of 2020! A total of 7500 IGNIS will be distributed daily to users running full Ardor and/or Nxt nodes!". I really hope they will continue with this reward program also in 2021 year, as this is still one of few things on ARDR blockchain, that make a perfect sense.
But now (for ca 12 hours) reward program is out of order -- maybe some technical maintenance due to new version of Ardor client (2.3.3) ? But I haven't found single word about this as here, as on ardorforum.org - where is till now also no single word about that 2.3.3 version in "Ardor Software Releases" section. This lack of communication thru the "classical channels" is sad.