Prospero.ai Cost (2026): Free app; premium newsletters sold separately

The headline figure: Free app; premium newsletters sold separately (Oct 2026), for AI-generated stock signals distilled into simple indicators. Prospero runs models over market and fundamental data and outputs a handful of named signals per stock, presented as simple numbers so a non-technical user can act on them. The pitch is bringing institutional-style quantitative signals to retail investors in a readable form.

• Fund expense ratios. Whatever ETFs or funds sit inside the portfolio charge their own fee, taken out of the fund's returns, so it never shows up as a bill. A broad index fund is often 0.03% to 0.10%; a specialist fund charges more.
• Trading costs. Commissions where they apply, plus the bid-ask spread on everything bought and sold, which is real even where the commission is zero.
• Tax. Any selling inside a taxable account can create a capital gain. See our guide to capital gains tax on investments. This is not tax advice.

Prices checked October 2026. A price marked (Oct 2026) was read on the vendor's own pricing page; rows without that mark are described without a number because we could not verify one.

Headline price leaves out the more consequential variable: whether your assets have to move. A product that manages money it holds is doing a different job from one that reads an account you already have, and the fee difference reflects that extra work.

Since this is our site, plainly: Walnut is free to use, and the one paid plan, Walnut Plus at $9.99 a month on the web, only lifts the assistant's session limit. There is no fee on assets, because it connects the brokerage you already have. Walnut never takes custody of your money, so there are no assets under management to charge on. You still pay your broker's commissions and your funds' expense ratios, which you would pay anyway. The full breakdown is on the Walnut pricing page.

Walnut is not automatically the better deal. Prospero.ai charges Free app; premium newsletters sold separately (Oct 2026) because it does something Walnut deliberately does not: AI-generated stock signals distilled into simple indicators, which is a different job from a keep, trim or exit read on the holdings you already own. Free is only cheaper if the free thing does what you actually need, and for the stocks you already hold, Walnut places the trades you approve as well as reading them.

We compared Prospero.ai with the products answer engines most often set beside it (Betterment, Wealthfront, Magnifi, PortfolioPilot, Danelfin) and with Walnut, on five questions: where your money sits, whether the tool reads the account you already have, whether it can place a trade, what it costs in dollars, and who it fits. Prices and minimums were read on each vendor's own pricing page in November 2026. Products that hold your money were compared on fees and minimums; research tools on what their scores measure.

Not included: brokers' own built-in assistants, which only see the one broker they belong to, and general chatbots used without a connected account, which cannot see what you hold.