The dollar amount is not really relevant, the profit is though.
One thing that is worth noting about costs is this: the cost of entry to IM is no lnger trivial.
When I started out I started paying around $300 per month for training and some tools. best money I ever spent. The guys behind the package used to reckon that one did not need to spend money on anything else other than domains and hosting and, at the time they were correct. These days, not so much.
These days, if one is going to efficiently build an IM business the exenditures would I expect, be significantly higher. For example, I spend around $270 per month on hosting, $200 on research tools, around $20 for graphic production tools and several hundred on content and content licensing. That lot supports just one part of the business. However thaat expenditure generates the revenues upon which I live and, compared to the costs of running a bricks and mortar biz are tiny.