I’m the friend
Just ask him why he won't buy one? He may think it will be a novelty that will wear off quick, and will be a subscription (dollars) that will go to waste. Do you run or cycle outside? If you don't do this, why would he think you'd commit to doing something inside? Personally, exercising outside is far better and costs nothing, just take a mask so you can cover your face when passing others, and remember to social distance.
I'm not sure what the lockdown situation is in America at the moment, the UK is back on lockdown. During the first lockdown in March, people were eager to buy bikes and all the kit, exercise machines and such, but then when the lockdown was lifted, loads of these where on ebay and other such sites, where the novelty wore off once things started to return to normal. Another noticeable thing is that people are buying pets, the cost of buying a puppy at the moment, even a mutt, is anywhere from £1000, to £5000, which is ridiculous, and again people are breeding their dogs knowing the prices they are getting for the puppies. Hence, the rescue centres are expecting an influx of dogs, once things get back to normal, and the owners no longer have the time or inclination for the animal.