Short: Zapertising
Long:
I used to work in digital marketing and growth as both a marketer and a programmer. The user acquisition cost is very high for traditional centralized platform/website/softwares.

In one of my job, a paid user cost us 3000 USD to get. Meaning, if this person don't spend 3000+, the company lost money. That's why many Silicon Valley style companies lose more money with more users before they reach monopoly and they have to squeeze money back from users at that point.

Because we separate the cost of client development, relay development and relay operation, it will be much cheaper to do digital marketing here.

For example, I can develop a advertisement platform on top of Nostr without paying the whole cost of the network, therefore I can charge clients (sellers of goods) much less and/or give ad watcher cash back from sellers' advertisement budget.

Now we have achived an impossible triangle in fiat world:
1. Lower cost for advertiser (ad distributor)
2. Lower cost for sellers
3. Get money to watch ads instead of pay money to block ads.

I believe this is a great way to get more users and I am actually working on getting some VCs interested in this plan. If we can use VC money to grow Nostr, it believe it's a net win.