Go to PirateShip and setup a free account (i.e., no monthly fee). Add your eBay account so you can import eBay orders.
Add a method to pay for labels. I suggest using a credit card with a rewards system so you get part of the cost of the label back as rebate from the credit card (typically 1%, 1.5%, 2%).
Go to Settings > General Settings
Set the Label Size to 4" x 6"
Set the Label Filetype to PDF
Packing Lists and Gift Messages to Disabled
This will create a 4" x 6" PDF document with a resolution of 300 pixels per inch (1200 x 1800) and you can download to your computer. In my case when I download a label to the computer from Safari it will automatically be opened by Preview on my Apple computer and I can immediately print it. I also have the option of printing multiple labels at once - I simply select them on and alter the print dialog window to print two per 8.5" x 11" sheet.
Because you have 300 pixels per inch to work with you can increase the printed size of the label a bit above 4" x 6" while still maintaining a crisp output suitable for scanning. For a full 8.5" x 11" sheet I change the print dialog window's layout setting to 2 pages per sheet. As I have Scale to Fit selected they are printed at 178% of the original 4" x 6" label using a monotone laser printer. If I am running a batch of tablet paper through the laser printer for labels I'll just print one label per sheet and select a different paper size.
Now if I would keep increasing the size of label it would eventually look blurry / pixelated. That is when you start to run into problems of a scanner being able to read the bar codes.
I would not use a bubblejet to print labels - they ink will cost you a lot money.
I am still using a monotone laser printer form 2001 and print all labels on paper, which are then taped in placed. I've replaced the drum one time as that was last year as I accidentally snapped off a small part. The high capacity toner cartridges are replaced every few years. The paper is left over from various larger lots of items purchased at auctions. Labels are cut out with a long pair of wallpaper scissors.
You can also go with a thermal printer but then you can't print other documents. It will require special label paper. The labels may fade over time without proper UB protection. The labels may not have the best adhesive and could peal off. Be sure to test some sample labels to see how well they stick on various surfaces.
