There is no reason to try to trick your prospect into buying from you. That isn't what professional people do. By trying to trick someone into engaging with you or buying from you, you destroy trust, thereby making the goal of becoming a trusted advisor an impossibility.
Built on a lie
If you type "Re:" in the subject line of an email in an attempt to have your prospective client believe that your email is a follow up to an earlier email in which they had already engaged with you, you are lying. How many positive, meaningful relationships do you have that began with — or were built on — a lie?
Your prospective client can easily search their email to discover whether they have engaged with you in the past, exposing you as someone who would deceive others to get what they want.
Deceptive practices
If you advertise that you provide a service for a lower than expected fee as a Trojan horse to trick your prospect into engaging with you about the more expensive service you really sell, then you are being deceitful. (There is an ad running on my Facebook where the "sales guru" suggests this tactic. He warns readers not to use this magical approach to do something untoward, suggesting that there is some purity to the method as he describes it.)