Arweave has a pay once, store forever model where after the initial payment to upload (~$0.005/MB) the file is stored forever on the permaweb. You can get started with some free tokens to play with arweave here:
I also suggest you check out the latest Arweave x Gitcoin Open Web Incubator Demo Day from last week to see the latest stuff being built. Looking forward to ArDrive, Verto, WeaveID and more.
https://www.youtube.com/watch?v=Slzyw1w5Ric&feature=youtu.be
One further advantage of decentralized UI hosting on Arweave is simply resilience to website outages: https://twitter.com/rleshner/status/1278444807011139585