The supporter money is also allowing anoek work full-time for the site and keep improving it, so its always worth that.
But to properly answer your question, if you have a good computer with decently good gpu and give leela time to make enough playouts, it will be stronger than that ogs can offer. The one still here is still an useful tool, it can provide lot assistance when reviewing your games.
If you can afford it, I would recommend to try it for 1 month.
You can cancel your support if you don’t think it’s worth the money.
As already mentioned OGS is only income are site supporters.
To me (12k), the 3€ AI gives a decent result as well.
You can always trade computing power against time. (Leelaz can run cpu only as well in case your gpu is really bad.
On my notebook cpu/gpu I get something like 20 playouts per second if I recall correctly.
Anyone with a modest gpu like a GTX 1050 or better should be able to enjoy as strong a review on their own pc. If you don’t have a decent gpu, the AI review could be worth it. Even if you do, the AI review still has some advantages:
One-click reviewing (no set up or expertise required)
Review games in browser (no downloading game records)
Custom interface not found elsewhere
Review attached to your games
Permanent link to review
Easy sharing with others
Can discuss with your opponent after the game
Good feelings supporting OGS development and the anoek household
You can always start at 1 euro and see if you like it.