My model has pegs on the back that will hold 45 pound olympic plates diameter wise, but you have to offset it from the wall a bit to account for the plate.

There’s been a lot of “you can try this” and “maybe” sorts of advice in this thread, but here’s something more concrete: smaller plates are going to be easier to move than larger ones, and the larger (weight) ones have to be larger (size) than the smaller ones (size and weight). You’re going to find more 45 pound plates than you will 100 pound plates if you’re shopping for them and more ways to store the smaller ones than you will the larger ones. You’re also going to want symmetry to whatever extent possible, so two 45 pound plates is better than one 100 pound plate.

The last time I was in the game I would look for $/pound. At that time, there wasn’t anything better in this metric than regular olympic plates unless you’re in a training montage set on a farm or in the woods. They tended to be a little more than $1/plate before tax. Now they’re more expensive because everything is, but they’re cheaper than stuff like kettlebells or fixed sized dumbells if you’re just considering “heavy” as your metric. If you go that route, then you have some more things available to you in your ecosystem, even if you’re not interested:

• https://www.academy.com/p/sunny-health-fitness-20-in-olympic-single-dumbbell-handlebar-with-ring-collars
• https://www.academy.com/p/cap-barbell-300-lb-olympic-grip-weight-set
• https://www.academy.com/p/cap-barbell-solid-curl-bar

Those choices are specifc based on the following points: the locking collars on the dumbell bar can NOT be the simple spring type as they’re not strong enough to hold the plates in various orientations. The curl bar gives you some flexibility for width if you’re in a confined space for deadlifts. (EDITED for correctness): The 300 pound set is $1/pound PLUS a free bar if you want to think of it that way if you count the bar, and I have seen those sets go for $250 making them the most economical weight set I know of. It helps if you have a local place because shipping is hell for this sort of thing. And all this just to hold down your pull-up rig. Now, I checked my PR-1000 or whatever it is. IF one were to lower the safety bars to their lowest setting, then the 45 pound plates that I have (they have little rubber bumpers) barely do not clear the bolts holding the frame together. A 35 pound plate on the lowest setting or a 45 pound plate on the next lowest setting would easily clear those bolts. The safety bar is 1" in diameter so a regular plate might fit on it, but the olympic plates are more of a guarantee and more standard. The back-to-front inner length of my rack is a little more than 25", and a 35 pound plate is around 1.25" wide, so with an infinite budget and against manufacturers recommendations (it says the PR-1100 can’t be bolted down and isn’t recommended for kipping up) we can get 20 35 pound plates (700 pounds) low to the ground per side, but 25 pounds plates might be more long term flexible. That moves the problem away from whether this MacGyver contraption is going to flip on you to the structural limits of the rack and the floor it’s sitting on. Note that anyone reading should follow the limits specified by the manufacturer and should also follow local building codes about how much weight they can put on a floor.

So, takeaways:

• I think your requirement set and price point doesn’t leave you wiggle room, but it gets close. You might try eyeballing tree limbs in your location, or exploring free options. The bodyweight exercise community is probably worth exploring.
• With the rack and the 300 pound weight set, and some abuse of manufacturer’s intent you’re going to come in over budget, but not as badly as I was thinking going into this. It’s would come down to tax and shipping to see how badly you blow the budget. If rack + weight set is too much, you can onesie-twosie the weights as money constraints allow. Just spread the weight out as much to the corners as you can, and keep it symmetric. If the rack doesn’t shift on you, stop adding weights.
• For basic pullups like it’s designed to do the rack will be fine out of the box. Trying to account for more dynamic exercises adds subjectivity to the thought exercise to account for every possible movement you might make, and that’s why this whole thread is wildly overthought for doing pullups.
• Nothing discussed here ever goes bad and has resale value that should be close to what you pay for it depending on local market. For that matter you can start eyeballing local used markets for the olympic plates. The thought exercise and working out on a spreadsheet costs nothing but time.