Don't look at the price
Of course, buying a bigger amount of office chairs might be expensive, but looking only at the costs of it will bring you nowhere. Making a good, ergonomic chair is costy, so the producer won't sell it on the verge of profitability.
If you're just opening your business or struggling to pay all the bills in the current one, try to on the verge of profitability. For example, you can buy a few chairs every month, gradually replacing all old, uncomfortable models with new, ergonomic ones. You can find really good chairs, which are safe for you and your workers at https://www.staples.no/c/stoler/ct-2678599.
Check out the material
When picking up ergonomic chairs for you and your employees, think about how they will be used. Probably each and every of you and the people you employ tend to get up from it at least a couple of times per hour. Bringing papers to another office, checking something out with a colleague, eatinga meal, getting a drink or simply visiting the bathroom - those are the things, that make you all sit down and stand up several times a day.
Thus, the material should be durable and abrasion resistant. Otherwise, the chair will simply cease to look aesthetically after a maximum of several months, which is not what you want.
What does "ergonomic" mean?
An ergonomic chair allows you to keep a healthy, safe position during your working hours. It also should be easily adapted to different people - as it's hard to imagine to only hire employees with average height and the length of the legs or arms.
To keep a safe, comfortable position, one should be able to reach the floor with both feet fully. Not with toes or heels, but with whole foot. In order to do that, the chair should be adaptable. This way, the the length of the legs or arms.
Home office chairs should also have armrests, which will allow you to keep a good position when working on a computer or writing something down by hand. The backrest is no less important than other parts of the chair. If you want to keep your back comfortable, pick a chair with backrest in size of letter "s". This way, the lower back of person sitting on the office chair will be properly supported, which will allow to avoid pain.