Of course. Tube amps are the sound of rock and roll.
You can of course pay any amount for an amp and cabinet.
Modelling amps have become ridiculously good, and given they can model just about any high end tubeamp straight out of the box, they are great idea for someone learning and playing different styles (assuming he is.)
Needless to say, your son is showing early signs of GAS - gear acquisition syndrome. This is a permanent affliction sadly. It can be treated for a while with purchases of pedals, amps, and guitars. But the symptoms always reappear, and there is currently no known permanent cure.
Loud is bad. Tube amps tend to only sound really good when they are at full tilt. If you have a powerful amp that means silly loud. Unless you need the amplifier to deliver sound into an audience, the smaller the amp the better. For practice, recording, or performance with the amp mic’ed and run through the PA, you want small. It has become common for many boutique brands to offer very low per amps, and amps with various forms of power reduction.
The amp you linked to has two pairs of EL84s. That is two too many. One pair, and an output of 15 watts is more than ample, and will still get insanely loud. The build quality looks pretty mediocre.
The speaker used is important. A very common upgrade for any cheaper cabinet is to swap out the loudspeaker. It has a significant effect on the sound. I say “speaker” and not “speakers”. There is again no value and only downsides using more than one speaker.
To get him on the right path, point him to five watt world https://www.fivewattworld.com/
If he (and you) are up to it, I would seriously consider a kit built combo amp. Its a pretty significant amount of work, but anyone can do it, and you get a hand built, point to point wired, tube amp. Which is serous money boutique amp territory.
The absolute perfect amp to build is an 18Watt. (That’s its name.)
https://www.18watt.com is the enthusiast forum for builders. There are quite a few kit vendors. The amp is based on the classic Marshall 18 watt.
A nice writeup of kits building The Mean 18: British-Style 18-Watt Amp Kits from Mojotone and Tube Depot - Premier Guitar
A kit is less than the Monoprice amp linked to, up to 50% more depending on parts and vendor.
A fabulous resource for amp builders, especially low power high quality sound is Guitar Amp Builders Forum (which used to be the AX84 site.) There are a range of kits available and lots of support and enthusiastic builders and players.