Depends where you, are but Probikekit with easily Googleable voucher codes is usually a safe bet for cheapest GX. In my case my LBS priced matched against that.
Some quick ideas on lighter, better value SRAM AXS...
Garbaruk cassette is in place for me and seems the easy choice for quality, value and lighter than 12 speed XX1 weight.
XO chain is 2/3 the price of XX1 and seems to be lighter compared to XX1 by a few g's, only lacking an aesthetic colourful final coating and otherwise being the same.
Loads of chainrings drop some g's and are cheaper than SRAM. I'm using Works Components for the best balance of quality, weight and value I have found.
I will keep looking in to the best g/£ weight loss on the GX AXS mech. I am trying to find the XX1 inner and outer cages as spare parts to maybe lose even more than Garbaruk for similar money but no luck on finding both. Garbaruk/ Ratio seems like the only real value option for eating in to that 460g rear mech weight
Definitely better than buying X01/ XX1 rear mech though for AXS
Any thoughts on jockey wheels which drop some g's for not too much money?