...is the seven thousand pictures I have taken since first contracting it in March of this year. Yes, that approximately corresponds to the date I joined this forum. Yes, I blame you lot - a little. But I was on the verge of buying the Sigma 18-35 Art lens, which (judging by the experiences of some on this forum) could have been a horrific mistake, and the forum spared me that.
I'm sure I've spent much, much more than that since, but I also think I've had a lot more fun for the price.
FA28/2.8, 50/1.4, 135/2.8, 28-90/3.5-5.6 - an autofocus three-prime set with backward compatibility to film bodies, and a cheerfully light and compact zoom with a good range for travel.
SMC or Super Tak 28/3.5, 35/3.5, 50/1.4, 55/2.0, 135/3.5 - started as a Takumar mirror of the above for my K-5, but then I got a Spotmatic and the need to expand the repertoire grew.
Pentax-M 80-200/4.5 - to duplicate the function of an heirloom that's not working so well
Bushnell M42 70-220/3.5 MACRO - for a fast M42 zoom that's good for everything from the birds to the bees
Samigon M42 135/2.8 - my first venture into M42 world; cheap and obscure, but not at all bad.
Pentax DA 18-135/3.5-5.6 WR - this one is the stand-out exception to the bunch; nominally used, but in fact it came in the box with all its paperwork and might as well be regarded as a new lens. Bought strictly and only as a WR option for bad weather.
Ricoh (K-mount) 55/1.2 - because everyone eventually wants to know what the f/1.2 fuss is about.
(pending arrivals, unclassified; further to follow)
As you can see, there's a role for everything. There's not much left in the way of "because I want to"; the only things I can think of are a vague wish for a DA15/4.0, a Pentax-A 50/1.2, and an FA31/1.8, if all can be had at a stumble-across bargain. But they can wait until opportunity knocks.
Infinitely more fun than buying the Sigma Art and resting on my photographic laurels.