If you solve a problem well, and it is a problem worth money to people - you can throw out some links on a forum or buy $100 in adwords and get a user or two.
A good advertising or marketing guy will help you go from 100 users to 1000 users, but you shouldn't need them in most cases to get a few users and start the path. Adwords isn't rocket science.
Now obviously there are exceptions, say if you are trying to create a 2 sided marketplace it's not so easy to just slow roll your product... but I think that is a fairly low % of total products.
A good advertising or marketing guy will help you go from 100 users to 1000 users, but you shouldn't need them in most cases to get a few users and start the path. Adwords isn't rocket science.
Now obviously there are exceptions, say if you are trying to create a 2 sided marketplace it's not so easy to just slow roll your product... but I think that is a fairly low % of total products.