That is simply not true. 12-15 lakhs is a VERY mediocre  wedding. Why? Well I'm from a upper middle class family, I've had 4 of my cousins that got married in  Nepal the last 2 years-both of which I have flown to Nepal for. My thulima told me the first brother that got married's wedding was 'decent' cost her 50 lakhs. Here is the breakdown:

Radisson ma party: drinks/food/ decor everything included 25 lakhs (had lots of guests mind you)
Dulhai ko ghana: aba this depends on your family tara in my family its 9 sets minimum (some are smaller sets that cost 2-5 lakhs some are bigger 5-12 lakhs)
Now one diamond set from ganepati jewllers or other recognized brands are around 11 lakhs for a bigger piece.

Dulhai ko luga: Listen every women in Nepal wants Oodhani boutique or other famous boutique ko luga. For a heavy bridal saree it starts at 25000 rs to 60000. Aru ta ja pani kiney huncha but for the engagement,mandap and reception you will need very heavy pieces.

That was on the decent end. My other cousin brother got married recent and spent nearly 2 core (he was the only son). Depends on how lavish you want to make the engagement, akal people have starting doing mehendi and sangeet too. But honestly you dont need to do all that. If you JUST concentrate on diamond sets/gold sets, clothes that she wants to wear not what your mother has picked out for her and a good reception at Radison or Soltie it should be good.

My guess: atleast 40-50 lakhs.