In percentage of GDP, or in absolute value? The latter would be difficult to believe; they're at over 150 billion USD per year.
In absolute value, but only considering the specifics.
Procurement spending 2021: (Capital budget)
IAF = $7.5B
USAF = 22.9B
The rest (Revenue budget), $153-22.9B = salaries, RDT&E, operations and construction, basically nothing that adds directly to capability.
Take the USA's (army) 2022 budget for example:
Total = $172.6B
Procurement = $22.4B
RDT&E = $12.8B
O&M = $69.3B
Salaries = $66.2B
Construction = $1.2B
The IA's procurement budget for 2021 is $5B. That's merely 4.5 times. You buy stuff for modernisation using the capital budget. It's obviously dumb to compare everything else to the IA's capital budget, right?
So IAF's can easily climb to $12+B before 2027, that's a little over half that of the USAF's 2021 capital budget.
In fact this is what I have been saying for the longest time. Russia's overall capital budget is $30B, which is enough for them to begin matching America's capital budget as long as they double that over the next 5-10 years. You will quite literally have another American military in your backyard by 2030. And it's really mind-boggling to me that no one in the West even talks about it, and those that try to make sense of it fail quite miserably. "Why is Russia buying Su-35 at $20M, didn't the Chinese buy it for $80M? I'm confused". It's more or less a case of the privileged being blind to their privilege. Money simply doesn't have the same intrinsic value everywhere. You can already consider that the Russian army and air force budgets match USA and USAF's, they don't need to match the USN's. Pentagon leaders have been saying this for quite some time now.
So the difference in procurement budgets between the IAF, IA and IN are 3, 4.5 and 13 times compared to the US' service branches. The USN's budget skews the perception because only China can match them today. The answers lie in the specifics, not the general.
IMHO, the IAF's capital budget should peak between $12-15B between 2027 and 2030, at about half the USAF's budget. The IA's should actually match the USA's budget between 2030-35. The IN's budget depends on our priorities. Otoh, R&D budgets should increase drastically with the entry of the private sector. Today, pretty much all of our R&D goes through DRDO, so the forces don't spend a lot on it. PPP will begin factoring in with indigenisation compared to our import-heavy procurements today. We are aiming for a 90-10 ratio by 2030. Parrikar had also said that our defence budget growth can be cut by half with import-substitution. So the peak may happen even faster.