Demo units are for those who are looking for bargains and are willing to buy used stuff. It's definitely not for everyone.
I remember many guys in Pdvd got their first HDTV's from the pier (me included ), and for sure the display units posted above are far better.
The really worst deals, imo, are the OLEDs from HMR. One month warranty on either display, refurbished, or RMA'd units, which is why I don't post them here.
Price is the same whether cash or installment at 0% interest. The latter is actually a marginally better deal; net present value and all that. But you do incur debt, of course, so you shouldn't be behind on your payments.
I remember those days that we scour the Pier for TVs. Kasama ako dun. I remember we had a seller here sa pdvd na taga Proj 4 QC. He was VERY passionate (to put it positively) about his wares and methods. I don't remember his name though but I hope he's doing alright.
I would slightly disagree with what you mentioned about the cash price being the same as card prices (including present / future value).
Salesmen will give you the "cash discount" off the bat pero it's not their best offer. Keep negotiating down and you might eventually get a much better deal.
I remember my Sony 65 4k ("J" series yata, I don't remember) from a couple of years ago. Card price was 95k. Cash price daw was 80k. He kept lowering it to 75.... eventually we settled at 69k.
Brand new, full warranty, sealed, we tested at the store (Cash and Carry), and I brought it home. Still works well to this day (it's been 4 years yata? Maybe 3?).
Parang bumibili lang ng relo yan. They give you a "cash price" daw but really there's so much room to negotiate. If they give you 10~15% off, don't take it. Keep going. If they won't budge, move on to another salesperson.