It's still not earning you money to spend electricity because you still have to pay the transfer fee which is around 6 cents / kWh but it's pretty damn cheap nevertheless, mostly because of the excess in wind energy.
Last winter because of a mistake it dropped down to negative 50 cents / kWh for few hours, averaging negative 20 cents for the entire day. People were literally earning money by spending electricity. Some were running electric heaters outside in the middle of the winter.
Or just export it - there must be nearby counties that don't have such a good renewable electric situation.
"just export it" sounds so simple, but the required infrastructure is actually incredibly expensive. Also most of Europe is already pretty tightly connected and trade does happen to a significant degree, but I have no idea what the actual percentage is or if it's used to balance oversupply and/or shortages. Kinda hard to find reliable sources for that.
Luckily, several interconnects already exist and more are planned.
As to percentages, most electric grids will publish those - for example FinGrid's current status.
Or water batteries for dams if your neighbors don't need your surplus, this way you don't need to extract lithium to produce regular batteries to store the surplus
https://www.science.org/content/article/how-giant-water-batteries-could-make-green-power-reliable
Lithium isn't going to be the way to store electricity on the grid. I wish people would stop bringing it up.
There isn't going to be a single thing. Pumped hydro, flywheels, sodium-ion, flow batteries, and heating up sand all have a place.
and who will you sell it to? the other countries will be building their own infrastructure eventually and they'll be trying to sell to you.
You sell it to places with different weather conditions (or as noted, to places with storage capacity) - and if everyone in the grid becomes as successful as Finland, well "good job, everyone!"
The "places with different weather conditions" are across the equator. Everyone in the northern hemisphere has summer at the same time. The best we can do with interconnects up here is shift the problem around by a couple hours.
Now, if we convert that excess power into cryogenic hydrogen, load it aboard a tanker, and drive that tanker to the end of the earth currently experiencing winter, they can then burn it in gas turbine generators.
Hell, we can put such generators on ships and move them back and forth every 6 months.