My bike is 7 years old, so the battery only has about 50% of its range. If I run it at its lowest power level, it can easily get 30km, I haven't pushed it further than that. If I bump it up to higher power, it drains pretty fast, but if I invested in a spare battery, it wouldn't be an issue. However, the battery for my bike model (an old easy motion) is integrated into the frame, so it's crazy expensive. More than buying a new and better e-bike. My bike also has v-brakes, which seriously sucks. Stopping quickly is NOT fun.
I googled Easy Motion and see a lot of different models, they all look "integrated", but only one looks completely sealed into the frame. (As in not removable at all), but even then, I think there should be a removable access panel.
If you can open up the battery, you might be able to see what kind of cells they used. Almost certainly they are the very common 18650 type. (18mm in diameter, and 65mm in length.)
If that's the case, it should be possible to count the number of cells you have, and buy a $20 12v spot welder, and some nickel tape, then look for the right cells to replace them. 18650 cell tech has come a VERY long way in 7 years due to Tesla and Vapers, both who use cylindrical cells of some sort.
When buying cells, they broadly cone in two types - energy dense, and power dense. Energy dense will give you longer range. Power dense will give you more... well power up hills and acceleration. It's always a trade off between the two and thankfully among the A grade manufacturers, (Panasonic, LG, Samsung, Sony, etc.) They all have a range of models between "2.2Ah, but will deliver all its power safely within 4 minutes" to 3.6A, but should be discharged no faster than in 30 minutes".
Genuine cells should be about $4-$8 usd per cell depending on volume. Most factory made eBikes would use 20 to 40 18650s, so the whole project cost should set you back under $300.
If you have done it before, you can probably do it in less than a day, but finding the right cells, double and triple checking everything will take a lot longer. Some eBike shops who actually service them, not just sell them can also do this for you for quite a reasonable cost. I'm not in the US, but on an eBike forum that has a lot of members that are, and it seems like those that get someone else to rebuild a custom pack, is about $400 to $500, but the people on the forum tend to do upgrades rather than straight replacements (bigger packs or higher performance packs) so it might be marginally cheaper.
I think the more people who can self service eBikes the better. While I encourage all eBike use, because it reduces emissions dependence on oil, and also creates a culture where biking issafer, it does shock me sometimes how much factory made eBikes cost (some as much as a new mid range motorcycle), and how much they try to lock you into their ecosystem and kept getting bled.