I agree that Commerce Kickstart is too advanced for what you need. You'd end up spending a lot of time configuring "off" a lot of stuff just to give your users a simple checkout.
I've setup several simple custom payment solutions for Drupal sites using Webform and Stripe.com.
Here's an example of a Stripe/Webform component: https://drupal.org/sandbox/jlyon/1472346
Not quite plug and play but also not a lot of development time to get a solid working solution.
Edit: You mentioned PayPal – you could provide that as an alternate purchase opition and use a simple paypal button to send them on their merry way; also https://drupal.org/project/webform_paypal
Edit 2: After thinking about Ryan's comment a bit, I would suggest you first grab Commerce module and tinker with it for a while. You may find that it gets you what you need. I have really enjoyed implementing some custom, lean payment systems using Stripe where a traditional "checkout" workflow wasn't appropriate, but there's no need to reinvent the wheel if it fits.