That sounds about right for light packages, but once you start adding weight they do get pricier. I use PayPal's semi-secret "Create a Shipping Label" page, and generally spend about $3 per envelope (it includes a slight discount over USPS's published rates)... but if I put in 13oz, it says $5.

13oz would be a lot of seeds, though!

You'd likely be fine just taking a guess and paying $3.25. I've never had USPS reject a pre-paid label.

I ship up to four packets inside a greeting card with a regular postage stamp. Can’t do this for bulky or heavy seed like corn, peas and beans because it has to be under 1/4” thick and not too heavy, so I just don’t trade those. Works for most flowers, herbs and veg.

Passiflora Collector yes, I often do this. If they're a bit bulky I add the 2x2 inch cut out of bubble envelope inside the card.

Also depends on your post office. The one where I work is so friendly. The post office where i live acts like they're doing you a favor to come to the counter.

Thanks for your good information.

Heidi