I have a Mini Cooper (that's it under the snow - Winter IS Coming). Great car. Over 100K miles on it and I just keep putting oil, gas and tires in/on it and it just keeps going (knock on wood). I've also had a lot of cars - not like a Jay Leno lot of cars but a regular amount I guess. Here's the twist though - when I bought my Mini, one of the things that I got was a username/password to the "Mini Owner's Lounge"...then when I was driving around, I noticed that other Mini drivers would wave...it dawned on me that I was part of a community.
So let's fast forward to now. The car does have a lot of miles and I am looking around but now I have a different decision to make - do I not only buy a new car (other than a Mini) and if I do, that also means I have to leave a community...I have to choose to not be a "Mini Owner" anymore.
How many people do you think feel that way about your products? Do your clients feel like they are part of a community? Do you think that it would be difficult for them to leave because they feel so linked to you? Let me ask this a different way - what is the cost (your sales team should know this answer) for your company to acquire a new client and what is the cost to keep an existing client?
So when someone asks you what the possible ROI scenarios are for training - think about crafting a response that includes customer-facing efforts to train/educate your customers...then <gasp> think about letting your customers train/help/educate each other...help them build a community that'll be hard for them to leave. Become social don't just do social.