It's the worst event you could ever fall for. Shinso Gin for 1 week is 840 gold or $20 now to own gin is 20K gold or $500. Now you can keep renting them long after the event is over. But there's a catch to renting anything it's going to cost you more than just buying it staight out. 1 month or 4 weeks 840 x 4= 3360 gold or $84 now let's do 3 months or 12 weeks
840 x 12= 10,080 or $252. now a year or 52 weeks you would spend 840 x 52= 43680 gold or $1092 twice as much as it originally costs.
White Ichigo is $1000 buying to own now renting for a week is 1680 gold or $42 now in 1 month it's 6720 gold or $168 3 months is 20160 gold or $504 and 6 months is 40320 gold which is $1008 $8 more than the original price that's just 6 months not to mention whatever lvl you had these characters or modified them if you do not renew them they reset.
this formula goes with every character in the limited lease.
gold x #Weeks = total gold /40 =$
lets not forget if u get partners in 1 go in different events that reward the partner as an item to redeem they start at lvl 1
but even if u only lease it for 1 day then buy it somewhere else in a different event that 100-400g saved u about 110lvls worth of gold skill books
to answer your question i have not rented a partner because of my prejudice of renting to the real world. I failed to realize that a lease is not renting but it's the very definition that you gave it's until it's paid for. That puts things in prospective for me. but at the same time troubling for the more expensive characters. However the drawback remains you still need tavern characters if you can't renew the character for long periods of time. But still These prices of things need to be cut dramatically. I don't know how much it costs to run this site and all it's departments to have such pricey things that won't even help you in the physical world. I always say buy a used car it's a better investment than spend money on this site but again if everyone had this insight this game would no longer exist and we'd be looking for a long term game to pass the time.
have you even rented 1 before, I ask because the moment you rent it the total gold needed to buy one starts counting down with every rent you make so in fact your formula is rather flawed because your basicly renting them till you can pay them off at their regular price which alot of people can't aford right out in 1 go. This event gives those people the chance to get the event partner in payments rather then spending over 300$ in 1 shot. The moment you reach the regual price in gold you get the partner permanetly.