Indeed there is an interesting aspect to comparing the regular and the kosher editions from the same winery over a period of time. My tasting notes follow, paired for easy comparison.
As to pricing fluctuations, my only guess would relate to supply and demand. For a more informed answer on that you'll have to consult with someone who understands the worlds of economics far better than myself.
Chateau Leoville-Poyferre, St. Julien, 2000: Deep garnet with orange and purple reflections, full-bodied, with firm but well integrated tannins. On the nose and palate cassis, red and black berries, spicy oak and appealing herbaceousness. A superb effort. Score 95. (Re-tasted 18 Feb 2005)
Charteau Leoville Poyferre, St.-Julien, 2000 (Kosher Edition): Full bodied, this deep garnet towards purple wine offers up generous almost sweet cassis and currants on a background of vanilla, smoke and light earthiness. Long and tempting even now but the tannins need some time to integrate. Best drinking will be from 2006 – 2012. Score 92. K. (Tasted 14 Jul 2003)
Chateau Leoville Poyferre, St.-Julien, 2001: Dark garnet towards purple, medium- to full-bodied, with soft, well integrating tannins and with generous wild berry and red currant fruits. Well balanced, with a generously spicy personality. Let this one develop and it will show chocolate, vanilla and a hint of cigar tobacco. Best drinking 2008-2016. Score 91. (Retasted 28 Apr 2004)
Chateau Leovile Poyferre, St.-Julien, Kosher Edition, 2001: Deep garnet red in color, medium- to full-bodied, with soft, nicely integrating tannins and generous aromas and flavors of plums and spices, those on a nicely spicy background. A long, blackberry finish here. Best drinking 2004 – 2009. Score 88. K (Retasted 22 Sep 2003)
Chateau Leoville-Poyferre, St.-Julien, 2002: Quite good but not showing quite as well as during barre tastings. Full-bodied, with soft tannins and berry and black currant fruits. As during barrel tastings still showing minerals and spices but with the wood rising on a too-short finish. Perhaps going into a dumb period so definitely to be re-tasted in the future. Best perhaps starting in 2008. Score 90. (Re-tasted 27 Apr 2005)
Chateau Leoville-Poyferre, St.-Julien, 2002 (Kosher Edition): Dark garnet, full-bodied, with soft tannins and spicy wood integrating nicely to reveal currant and berry fruits and, in the background, pleasing undercurrents of spices and licorice. Best 2007-2011, perhaps longer. Score 89. K (Re-tasted 27 Apr 2005)
Chateau Leoville Poyferre, St.-Julien, 2003: Full-bodied and remarkably concentrated but now showing far more generous, complex and elegant. On the nose and palate black currants, blackberries, and plums, those on a background of caressing tannins and near-sweet cedar wood. Don’t dream of getting to this one before 2010 but think in terms of best 2012-2030. Score 95. (Re-tasted 24 Mar 2006)
Chateau Leoville Poyferre, St.-Julien, 2003 (Kosher Edition): The non-kosher edition of this wine is one of the stars of the 2003 vintage and this kosher edition, while not at that exalted level, is well worth considering. Full-bodied, with good concentration and with its firm tannins starting to integrate and opening to reveal ripe currant, black cherry and purple plums, those on a background of toasty oak. Long and generous but needs dime. Best 2009-2015. Score 91.K (Tasted 22 Dec 2006)
Chateau Leoville Poyferre St. Julien, 2004: Dark garnet towards royal-purple, medium- to full-bodied, with firm near-sweet tannins needing time to integrate. Opens on the nose and palate to reveal traditional black currant and blackberry fruits, those supplemented nicely by black cherries, toasty oak and, on the finish a rather generous hint of vanilla. Give this one some time. Best 2010-2020. Score 91. (Re-tasted 28 Mar 2007)
Chateau Leoville Poyferre, St. Julien, 2004 (Kosher Edition): Full-bodied, with firm tannins starting to integrate with hints and vanilla from the oak in which it aged. Opens to show traditional currant and blackberry fruits, those on lightly spicy background. Needs some time. Best from 2010. Score 89. K (Tasted 1 Sep 2008)
Chateau Leoville Poyferre, St.-Julien, 2005: Dark ruby towards royal purple, full-bodied, with soft tannins, fine balance and a delicate but well balanced structure. On the nose and palate an array of currant, wild berry, and toasty oak, those on a lightly spicy background. Approachable and enjoyable now but best 2010-2025. Score 96.
Chateau Leoville Poyferre, St. Julien, 2005 (Kosher Edition): Perhaps the best kosher edition ever from Leoville Poyferre. Deep garnet towards royal purple in color, full-bodied, with gently caressing tannins and just the right hint of spicy and vanilla rich oak. On first attack blackcurrants and blackberries, those followed by hints of blueberries and, on the long finish notes of lightly minted chocolate. Approachable and enjoyable now but best from 2010. Score 92. K (Tasted 1 Sep 2008)