A security-only audit for a small company with a narrow product focus can indeed be very inexpensive. A full SOC 2 examination for a large organization with a mix of legacy and modern systems by a name-recognizable public accounting firm can be many hundreds of thousands of dollars, or more if you need a Big 4 firm.
In my opinion, there's not much value to the "cheap" audits... If you're doing enterprise sales to a certain kind of client, your partners who demand an audit are going to want a reputable auditor or they're just going to put you through their own in-depth procurement due diligence regardless. The segment of the industry where a SOC 2 attestation is mandatory to participate but where any random auditor will do feels pretty narrow.
My experience is the opposite of yours: having a security SOC2 ends the vendorsec process it any enterprise buyer, and enterprise buyers virtually never read anything in the SOC2 other than a glance at the exceptions. A very large, very security-intensive vendor we have all heard of told me a story about a vendor they had that gave them several years of repeated Type 1 reports. Went fine.