Before investing, developing a new product or service, never mind the cost of marketing; You need to see if the there is a market for what you intend to offer and whether the market is big enough to make it worthwhile. This is not easy and it’s often got wrong. Experts didn’t see a need for tablet computers, Apple proved them wrong!
It’s wise to aim for growth markets, declining ones are likely to be crowded with pricing under pressure.
Test marketing is one way, doing a survey another or you could host some workshops.