Avalonia XPF
What would rewriting your WPF app actually cost?
Put in your own numbers. The method and every coefficient are on this page, so you can forward the result to whoever has to approve it and have them argue with the assumptions rather than with you.
Your application
Windows, pages, user controls and dictionaries. Count them with: find . -name '*.xaml' | wc -l
Changes how long it takes, not what it costs. The total effort is the same.
Fully loaded cost per engineer-day, including employer taxes and overhead.
DevExpress, Telerik, Infragistics, Syncfusion, Actipro, SciChart and similar.
Rewriting it yourself
€227,500 to €612,500
Roughly 9 to 24 months of calendar time with 2 engineers on it, during which that team ships nothing else.
A rewrite costs 7.7x to 20.8x the XPF licence, and at the end of it you have the feature set you already had today.
XPF needs no contingency buffer for third-party controls, because it does not touch that code. Your existing suites are WPF controls, and XPF runs WPF.
What this calculation assumes, and what it leaves out
Effort is estimated at 1 to 2.5 engineer-days per XAML file. The range is wide on purpose: a file may be a twenty-line resource dictionary or a nine-hundred-line screen with a custom control tree behind it, and that spread is the largest single source of uncertainty in any estimate of this kind.
Where you have told us commercial control suites are present, a 30 to 40 per cent contingency buffer is applied. That figure is not ours. It is the buffer recommended by published scoping guidance for migrating WPF to other cross-platform XAML targets, which files commercial control suites under red flags that materially raise an estimate.
Calendar time assumes 220 working days per engineer-year and that the work parallelises cleanly across your team. That is generous. Migration work has real serialisation points, and adding engineers to a late rewrite is the textbook case where it does not help.
Not included: QA and regression testing, re-certification or compliance sign-off, retraining, documentation, the cost of defects that reach customers, or the revenue effect of a roadmap that stopped moving. Each of those is real, and each of them pushes the number up rather than down.
Want the real number instead of the estimate?
Bring the actual codebase. We will scope it with you, tell you what XPF does and does not handle in your specific application, and tell you honestly if porting to free Avalonia is the better answer.
XPF is a binary-compatible WPF runtime. Your XAML, your code-behind and your commercial control suites come with you, and you change one SDK reference.