The whole question is how much would what level of "friendship" cost China. Imagine a full alliance, kind of US enjoys with Japan, where Japan gives bases. Imagine Chinese bases all around Philippines and how much that would be worth. Granted, that may not cost just 10 billion a year but more.
Point is, having access to extra bases farther into Pacific is of such immeasurable worth militarily wise that monetary price can't really put on it.
A) it threatens Guam with a wider range of weapons, as distance from nearest bases is now 2100 km.
B) it threatens Taiwan and Okinawa from an additional direction, complicating their defenses.
C) it secures SCS and south Chinese coast to a much greater degree.
D) it ties up a lot more of US assets as US suddenly has to keep monitoring the entire area between first and second island chain.
E) it basically gives PLAN proper access into pacific, with a fair chance of survival for it's various submarines as they are entering it. (Both for ssn and ssbn) That in turn ties a lot more us subs and assets to a vast area of pacific.
Basically, if compared to how much money is spent on various other stuff, including certain aspects of the military budget, the return on investment could be much, much better.
*IF* friendship can be bought with money. Which likely may not be the case. And certainly US would cry foul and portray such aid as something unholy and might respond with getting much, much more aggressive towards China.
A weak ally is worse than no ally, and one you can buy with money could just as easily be bought by someone else.
It was only a few short years ago when the US was signing agreements to re-establish their old military bases in the Philippines. What assurances would China have that the Phillipines won’t just flip flop back if America makes them a better offer?
The Phillipines is too weak and chaotic as is, if they swing fully into China’s camp and allowed China to set up military bases all over their territory, you can pretty much guarantee that the CIA will be throwing everything they have into staging a coup. Failing that, they will just light the fires for a civil war and keep throwing petrol on it until the whole place implodes like Syria.
Just look at how Russia was sucked into the whole Syrian mess to bail out their weak ally Assad. Going further back, America has also tasted the bitter blowback from failed attempts to prop up weak allies as was the case in the Korean and Vietnam wars. While the Soviet Union had similar nightmares in Afghanistan.
The Philippines is also too far from China, making supply lines for any Chinese forces based in country long and difficult to secure.
You also have to take into account all the other relationships your allies have, since such a strong embrace of the Philippines would almost certainly make the neighbours they have conflicting territorial claims feel like China is now going to take the side of the Philippines, which may cause them to also seek stronger protectors themselves.
If China was seriously worried about breaking into the Pacific deep waters, securing Taiwan would be a far far more worthwhile play. Might as well promise Taiwan $10bn in ‘aid’ every year if they peacefully reunite with the mainland. Or buy $10bn more arms every year in preparation for taking Taiwan by force.
If push comes to shove, China’s military options are far more robust in a Taiwan scenario than trying to prop up the Philippines government in the face of an American orchestrated civil war, and later direct US military intervention in said civil war, going by the Libyan and Syrian playbooks.
If anything, such an extended military campaign will likely weaken Chinese capabilities to take Taiwan by force if separatist forces seek to capitalise on China already being extended in the Philippines to declare independence.
Pushing deeper into the Pacific via the Philippines only really makes sense if China was seeking to try to take the fight to the Americans.
That is simply too ambitious for China’s military capabilities, and will be an unwise play for probably decades at current trends.
Besides, I don’t really see the point in obsessing with breaking through the various island chains.
China is building the SCS up as its SSBN bastion.
The SCS is large and deep enough to easily allow Chinese boomers to disappear, and the new gen SLBMs China is developing should give those boats enough reach to hit all of the US without having to leave the SCS.
That is a far more secure second strike capability than having your SSBNs playing hide and seek unsupported by friendly forces while being effectively surrounded by hostile ASW assets, as they would be in the Pacific.