I agree with Justin, this is a BUSINESS and your bottom line comes first - along with being ethical.

I always also put links to the upsell 1, in the followup messages and I tend to leave that a few days apart so the customer can get their value from the front end product FIRST and then make an informed decision whether or not to buy.

If they do, they return to the funnel and see the further upsells...

If they don't buy, then you repeat the followup message process.

Regards

Ray