We bought her a bubble tea and a birthday present, a coat from Zara, which to be fair was 1 day late. She asked the price of both. She also asks the price of random things in our flat- the sofa throw , random meals we mention we had outside, my backpack (which is actually the most expensive thing I own other than our flat), our salaries etc.
It is a bit embarrassing cos her mum, my MIL is very thrifty and also on a low income. She doesn't have a job herself. For example, my MIL thinks a coat should be from ASDA and cost £20 max but in reality my DH spent like £120 on the coat
I sometimes put my foot down and just tell her I am not uncomfortable disclosing how much I spend on things. But the line of questioning is sometimes relentless. I don't really understand why she does this? My DH thinks its because she wants to have 'control' over things.