When it would come in handy to be a gypsy

I'm currently trying to sort out (and very poorly negotiate a price on) our reception decor. I've watched those wedding shows on TLC where the brides talk the vendors down a few hundred dollars, but I always watch through squinted eyes, with my face in a full cringe. I've read that no prices are set in stone, but I just don't feel comfortable bartering over services. I think I'm also too naive in that I assume everybody will give me their best price without pulling the metaphorical wool over my eyes. When somebody says something is worth $400, I assume that it's worth $400, no less, and I don't get all sly and say, "ok....ok....but how about $300 for that AND the other fabrics?" It's not in my nature. Even when I've been in Mexico in the markets, I'm total crap at bartering...and if there were ever a place to do some hard core bartering, it's the markets in Mexico.

About five years ago I went to Cancun with four of my girlfriends and I learned a thing or two about one of them that I never knew: she can barter like a one-legged gypsy at a back alley rummage sale. It would go a little something like this:
"How much for this ring?"
"120 pesos..."
"WHHAAAAAT??? WHAT?? Are you KIDDING ME!!!"
....stunned look on the vendor's face, mouth agape...
"One hundred...and TWENTY PESOS!! WHHAAAAT??! ........I'll give you ten"
Vendor laughing hysterically.....
Then she works her gypsy magic and leaves with the ring for 20 pesos, meanwhile I'm at the stall next to her paying 350 pesos for my ring (that didn't fit when I got home and my swollen mexico fingers had unpuffed).

I don't expect to whittle every price down that's sent my way, but I would like to maybe make a decent negotiation here or there. I'm starting to realize though, that I'm the trusting type that can be easily swindled. BUT, I am also the type to try and make my own 60 foot chiffon swagged ceiling decor just to spite the vendor who wouldn't honour my request of $40 less!