I assume you would have to put in your secret key or give full access to the Stripe account? Both of which sound like giant red flags.
Also what exactly is a request? And pricing, how does $5 for 250 make sense? $5 to send 250 text messages?
Startups would put in their restricted key - a secret key with only the access that is necessary.
In terms of pricing, a request is an api call. I can see your point with $5 to send 250 text messages. It does sound steep. The first 5000 requests are at $20 which should adequate for most startups. Majority of our customers don't use more than 750 right now.
If we find customers maxing out the limits too quickly we will definitely adjust our pricing