Well, everyone has their own threshold and limits on what they feel is worth the money, etc. Personally, I think that handbags are worth it, especially in classic styles you can use for many years. I am not, and never will be, drawn to the trendy handbags that scream "Look at me! I'm from s/s '08!"
Most of my collection consists of flaps/reissues, but I do have one beautiful RTW jacket I scored on ebay, as well as some costume jewelry. If I were to pick between the three, a handbag would win the "what should I purchase" competition, 99% of the time. While I love RTW, the prices are ridiculous (for me), even though you are paying for a beautifully constructed item, a closet full of RTW, however appealing, isn't in keeping with my lifestyle. I love fashion, but sometimes you need to dress for the life you have versus the life you wish you had (haha, the latter part is not true, but I'm just saying).
That said, if I found a gorgeous RTW piece in exactly the colors/style I want (I'm very picky) AND the price was decent, I would consider it, sure.
So yes, a few gorgeous jackets you will use often (and preferably ones you found on sale) are worth it to me.
As for costume jewelry, I have a lot of cute necklace I purchased years ago, all for under $350. I also have a lot of earrings I purchased when prices were more... reasonable. However, those prices have gone to hell haha.
I'm guilty of spending an ungodly amount of $$$ on the makeup charms necklace this season, and I vacillate between thinking "What the hell were you smoking?!" and "Wow, it's such a pretty, fun, whimsical piece that real jewelry cannot take the place of!" I guess the last statement wins, because I plan to keep it.
While I do think that real jewelry is beautiful and happen to own a lot of it (my dad's family is in the jewelry business... I can only imagine what they would say if they saw my costume jewelry with the prices attached!
), sometime diamonds/real pearls, etc. don't work for me. I'm not going to wear real pearls/diamonds to visit friends, go out to a casual dinner, attend a class, or whatever. Real jewelry has its place, and for me, it isn't often that wearing it meshes with my life style (other than, say, diamond studs, or a simple necklace). I have four Chanel "pearl" necklaces I wear quite often (including the makeup charms one), and to me, they are the core of my costume jewelry collection. Knock on wood, I haven't had any quality issues thus far. So those pieces, yes, I would purchase again, but from now on, I've become much more selective. More money spent on non-bags means less money on, well, bags!