While it's not uncommon for the payment plan price to be more (when you total it up) than the pay in full price, having the payments be less than a month apart is very suspicious. The payment plans are basically financing without having to get a loan or something and are riskier than when someone pays in full. Her numbers aren't that bad actually $1497 vs $1794 would not be unusual in this scenario. You do it this way to make the pay in full option more attractive. It's a common marketing/sales tactic but usually the payments set to be once a month until all payments are completed...not within 2 weeks, that's ridiculous. And you're right, if someone put this on their credit card, then they're paying more interest on top and that sucks.
I see that Anna is still offering her "convenient" payment plan, which people here have posted before. It has always struck me odd that the two payments combined were so much more than the single-payment price. Also that the payments were a mere two weeks or 15 days apart. If these payments were charged, they could easily end up in the same billing cycle (or monthly budget allotment), thus offering no budget convenience at all. Now lets look at that higher price. $897*2=1794, which is a premium of $297 over the basic price of $1497. $297/1497 means a hefty 19.8 interest rate for that 15-day postponement. That translates to an astounding 481% annual interest rate! (Please feel free to check my calculations.) I have heard financial gurus warning against the hidden costs of timed payments (e.g., credit cards), but I have never heard of an interest rate this high. And if the purchaser paid for this on a credit card on which she was already paying high interest, she had better hope that a millionaire grabs her soon, or it will be off to debtor's prison.