When to offer a higher-touch, higher cost upgrade to a low-cost product?

Hello. I’m creating a self-paced online course (no interaction with me) that walks an aspiring writer through the process of brainstorming a book. This is not my main signature product – that’s a multi-month one-on-one book coaching package that costs several hundred a month. I imagined this online course to be a low-cost means (under $50) for potential clients to “try me out” and get some results ahead of time via progress made on their book.

Then I had the idea to offer an “upgrade” add-on to this product: a 30 minute book foundation one-on-one consult call with me once they’ve completed the course so they can run their ideas past me and ask any lingering questions. Naturally this would carry an additional price – but that could also push it out of the low-cost, trip-wire category.

The purpose of that call would be to give them feedback on their homework from the course. But I could also make an offer at the end of it for my monthly coaching program.

My question is at what point in the sales process should I offer the add-on call upgrade?

– Should I advertise the course with two options and price points – one with the call and one without – on the landing page and let them choose?
– Or should I leave mention of the call off the course upfront, but make the offer for a live call with me during check-out, or sometime after course purchase?

Wondering if you know of a rationale that makes one way a generally more effective move than the others? Thanks!