three tools already do this at $19 — is that validation or a closed door

Price similarity mostly tells you the ceiling everyone has already discovered. At $19 you need roughly 158 accounts for $3k a month, and if you lose 5% of them a month you need to add about 8 new accounts every month just to stay level. Write that number down before you write any code, because it is the actual thing you are signing up for.

The useful competitor number is not their price, it is their headcount. Check whether they are hiring, whether they have a careers page at all, whether the founder still answers support. A four person team at $19 needs many thousands of accounts and is under pressure to move upmarket. That pressure is where a solo person eats.

Three paid competitors at a similar price is the least worrying thing in your post. What would actually worry me is three free ones, or one that is free and venture funded.

The check that works for me is boring: pay for all three with a real card, then do one real job of your own end to end in each. Keep a notebook and write down every single moment you had to leave the tool. Exported to a spreadsheet, copied a value by hand, opened a second tab, asked a colleague, gave up. Those exit points are the map. When I did this in a different category I ended up with eleven exit points and nine of them were the same two steps in all three products. That was the product.

Also read their docs and their support pages, not their marketing. Docs tell you what they actually built. Marketing tells you what they wish they had built.

Competitors prove demand. They do not prove distribution. The question you have not answered is where your first thirty customers come from, and that answer must not be "search", because all three of them already own search.

I want to push back on the answer above about bad reviews being an opening, which is what people usually conclude from this exercise. Bad reviews on a mature product are frequently about things you will also have: billing edge cases, one integration being flaky, support being slow at scale. Those are not strategy gaps, they are the tax of running a product with real customers, and you will inherit them the moment you have more than fifty accounts.

The genuine gap is usually a segment, not a feature. Somebody the incumbent cannot serve profitably because of language, region, an ugly legacy file format, a regulator, or a workflow that only exists in one industry. That is the door. "Same thing but better designed" closes it on your fingers.

New-ish at this so take it lightly, but the thing that unstuck me was realising "is there room" is not answerable in the abstract. I wrote down one specific person I know who currently uses one of the incumbents, and asked what it would take for them to switch. The answer was "nothing, switching costs me a week". That killed my idea and saved me four months, which felt bad for a day and great for a year.

Cheap experiment before your ten weekends start: go find where their customers complain in public and read six months of it. Support forums, app store reviews, the replies under their launch posts, their Discord if they have one. Sort mentally into "wish it did X" and "it broke and nobody helped me". Two hours of that will tell you more than any framework.

Second thing, and this is the one people skip: try to buy from them badly. Ask a pre-sales question by email as a small customer and see how long it takes to get an answer. If a $19 product takes six days to reply to a buying question, you have found out how much they care about the low end.