I know of people who had a really nice car and home and yet got a smaller car and a smaller house for 'fear of stumbling others'. I wonder if this was prompted by the elders...
Having lots i suppose it not being materialistic, if you have for example a successful business but other things come first then i don't suppose you would even get any attention.
Fortunately i am not a JW and i don't have to worry about how well i do, but i know for a fact the society encourage people to keep their eye simple and even young people are encouraged not to go for big-time education. Instead do ministry all day every day (do some live off benefits...so basically the taxpayer keeps the witnesses?)