It makes a lot of sense to own equipment you regularly need, as you'll be the one making money off it, instead of the rental house. Prices of most rental gear is about 2-3% of its total value, so if you would need it over 30-50 times in say 2-3 year, it would be wiser to own.
Also, it depends on the average budget of your productions. Most of my clients will accept paying 200-300 Euro a day for my camera equipment. (So, that'd be total value of 15k euro max, at 2% 'rental' price and 300 eur a day).
With that budget I can afford to shoot on my Blackmagic cameras. No RED/Alexa however. Those I rent, whenever needed.