Price points are very much your choice and how you justify what you’re charging. Maybe using the Dan Kennedy style of comparing apples to oranges – he often charges the same for the DVDs of a conference as for attending the conference in person as you’re not travelling or paying hotel bills.
Build the value and deliver on it.
Dennis Becker started cheap and is still (I think) fairly cheap.
Sean’s are around $30 / month; Paul Nicholls has moved up to about the same price. I’m aiming for a similar monthly price.
Terry Dean charges (from memory) $67 /month for a reasonably short weekly insights video and access to a fairly sluggish forum.
Testing is the only real answer – and once you know the dropout time, consider sending an upgrade email at some stage in your sequence for a year’s worth of membership at a discount price that’s higher than you’d have got if they’d dropped out after X months.