I've been using Foundry with Forge for hosting for a few years now after using RealmWorks and Map Tool. I tested Fantasy Grounds, Roll20, and d20pro before settling on Foundry. Since then there are many more VTTs that have become popular and improvements made to the more popular ones, but nothing has been compelling enough to move me from Foundry.
I can't really claim paying once as a benefit because I pay to host my license. The Forge has been a big reason for my satisfaction with Foundry, allowing me to host games with people in multiple countries in multiple regions, even with sub-optimal Internet.
But I really appreciate not being locked in. I can move to another hosting provider or host myself and I back up my content offline.
It is also a bit of hobby in and off itself. If you like to customize and tweak, Foundry is the best of the VTTs.
Lastly, I'm really excited about the developers upcoming campaign system build for Foundry, called Ember, and their custom game system, Crucible. I've never been satisfied with Foundry's support for 5e. While they finally have a license, they still have a way to go. Foundry's 5e support can't hold a candle to the Foundry games systems for Pathfinder 2e or Warhammer Fantasy Roleplay 4e. I am really looking forward to seeing what they can do with a system and campaign developed specifically for Foundry, but the Foundry development team.
That said, I do feel it is on the heavier end of VTTs and tends to have a higher time demand in terms of prep. On the rare occasion I run a D&D 5e one shot, I use D&D Beyond Maps, which is a solid, lightweight VTT if you use D&D Beyond.
