https://www.esim4travel.com/europe-esim?p=ESIMDB

Esim4travel's Europe 7day 1GB is absurdly cheap at $0.85... BNEsim Europe 30day 1GB (auto renewal) is $0.99... again, along the lines of $1-2/GB in EU

Bnesim says they have auto refill option, haven't tried it though

If you travel to Europe often enough and don't mind juggling a little
1) bnesim noexpiry 5GB $10.89 minus $7 referral 986SNP3F = $3.89. 3GB $6.75 minus $5 referral 986SNP3F = $1.75
2) bnesim europe 30day or esim4travel europe 7day 1GB for <$1.
3) esim4travel Bosnia+Herzegovina

Keep (1) as backup esim, use (2/3).. if you run out of data on (2), or transiting through Europe, or having a layover, or having problems with (2), use (1)

Buy/topup (2/3) as needed

​​​​​​Noexpiry is twice the price of expire-able data. Probably not worth buying noexpiry in the long term vs the cheap 1GB versions?