ndee,
Thanks for the compliments (and also for the help before release in testing)
, and yes, you're correct, you pay only the difference, all options taken in account.
The automatic license upgrader calculates your upgrade price based on the exact difference between the price of what you have purchased and the new price if you would be purchasing. No fees, no offsets, no hidden costs. And a clear overview of your installed base.
It's ajax-based, so you can just go to your profile, click the button, and see in drop-downs the difference of cost for that particular item, then select the new item, and it will automatically re-compute the other costs, and display you the total if you would purchase the upgrade. You can then simply press the cancel button. No risk.
E.g. you could purchase a "1 site, 500 users, 1 year starter package", then upgrade it to "2 sites, 1500 users, lifetime maintenance". It will handle that fine.
Or you can just extend your 1 year maintenance to 2 years, or lifetime (the starting date of that license will stay, so it's a maintenance extension).
You can also have multiple licenses withe different options at same time. No limits, except maximum 10 sites each for now.
If you need more than 10 sites under the same license, contact me using website contact form